1. What is the output of the program given below
#include<stdio.h>
main()
{
char i=0;
for(;i>=0;i++) ;
printf("%d\n",i);
}
2. What is the output of the following program
#include<stdio.h>
main()
{
int i=0;
fork();
printf("%d",i++);
fork();
printf("%d",i++);
fork();
wait();
}
3. What is the memory allocated by the following definition ?
int (*x)[10];
4. What is the memory allocated by the following definition ?
int (*x)();
5. In the following program segment
#include<stdio.h>
main()
{
int a=2;
int b=9;
int c=1;
while(b)
{
if(odd(b))
c=c*a;
a=a*a;
b=b/2;
}
printf("%d\n",c);
}
How many times is c=c*a calculated?
6. In the program segment in question 5 what is the value of a at the end
of the while loop?
7. What is the output for the program given below
typedef enum grade{GOOD,BAD,WORST,}BAD;
main()
{
BAD g1;
g1=1;
printf("%d",g1);
}
8. Give the output for the following program.
#define STYLE1 char
main()
{
typedef char STYLE2;
STYLE1 x;
STYLE2 y;
clrscr();
x=255;
y=255;
printf("%d %d\n",x,y);
}
9. Give the output for the following program segment.
#ifdef TRUE
int I=0;
#endif
main()
{
int j=0;
printf("%d %d\n",i,j);
}
10. In the following program
#include<stdio.h>
main()
{
char *pDestn,*pSource="I Love You Daddy";
pDestn=malloc(strlen(pSource));
strcpy(pDestn,pSource);
printf("%s",pDestn);
free(pDestn);
}
(a)Free() fails
(b)Strcpy() fails
(c)prints I love You Daddy
(d)error
11. What is the output for the following program
#include<stdio.h>
main()
{
char a[5][5],flag;
a[0][0]='A';
flag=((a==*a)&&(*a==a[0]));
printf("%d\n",flag);
}
20. Output of the following program is
main()
{int i=0;
for(i=0;i<20;i++)
{switch(i)
case 0:i+=5;
case 1:i+=2;
case 5:i+=5;
default i+=4;
break;}
printf("%d,",i);
}
}
a) 0,5,9,13,17
b) 5,9,13,17
c) 12,17,22
d) 16,21
e) Syntax error
Ans. (d)
24. What will the following program do?
void main()
{
int i;
char a[]="String";
char *p="New Sring";
char *Temp;
Temp=a;
a=malloc(strlen(p) + 1);
strcpy(a,p); //Line number:9//
p = malloc(strlen(Temp) + 1);
strcpy(p,Temp);
printf("(%s, %s)",a,p);
free(p);
free(a);
} //Line number 15//
a) Swap contents of p & a and print:(New string, string)
b) Generate compilation error in line number 8
c) Generate compilation error in line number 5
d) Generate compilation error in line number 7
e) Generate compilation error in line number 1
Ans. (b)
In the following code segment what will be the result of the function,
value of x , value of y
{unsigned int x=-1;
int y;
y = ~0;
if(x == y)
printf("same");
else
printf("not same");
}
a) same, MAXINT, -1
b) not same, MAXINT, -MAXINT
c) same , MAXUNIT, -1
d) same, MAXUNIT, MAXUNIT
e) not same, MAXINT, MAXUNIT
Ans. (a)
What will be the result of the following program ?
char *gxxx()
{static char xxx[1024];
return xxx;
}
main()
{char *g="string";
strcpy(gxxx(),g);
g = gxxx();
strcpy(g,"oldstring");
printf("The string is : %s",gxxx());
}
a) The string is : string
b) The string is :Oldstring
c) Run time error/Core dump
d) Syntax error during compilation
e) None of these
Ans. (b)
What will be result of the following program?
void myalloc(char *x, int n)
{x= (char *)malloc(n*sizeof(char));
memset(x,\0,n*sizeof(char));
}
main()
{char *g="String";
myalloc(g,20);
strcpy(g,"Oldstring");
printf("The string is %s",g);
}
a) The string is : String
b) Run time error/Core dump
c) The string is : Oldstring
d) Syntax error during compilation
e) None of these
main()
{char p[]="String";
int x=0;
if(p=="String")
{printf("Pass 1");
if(p[sizeof(p)-2]=='g')
printf("Pass 2");
else
printf("Fail 2");
}
else
{
printf("Fail 1");
if(p[sizeof(p)-2]=='g')
printf("Pass 2");
else
printf("Fail 2");
}
}
a) Pass 1, Pass 2
b) Fail 1, Fail 2
c) Pass 1, Fail 2
d) Fail 1, Pass 2
e) syntax error during compilation
Give the output of the following program
struct XXX
{int a:6;
float b:4;
char s;
}structure;
size of (structure);
main()
{char *s;
s="hot java";
strcpy(s,"solarrs java")
}
main()
{char *p='a';
int *i=100/*p;
}
what will be the value of *i= 1
struct point
{struct point *next;
int data;
}
x;
main()
{int i;
for(x=p;x!=0;)
x=x->next,x++;
freelist(x);
}
freelist(x)
{free(x);
return
}
typedef struct
{char *;
nodeptr next;
} * nodeptr ;
What does nodeptr stand for?
Q2. What does. int *x[](); means ?
Q3. struct list{
int x;
struct list *next;
}*head;
the struct head.x =100
Is the above assignment to pointer is
correct or wrong ?
Ans. Wrong
Q4.What is the output of the following ?
int i;
i=1;
i=i+2*i++;
printf(%d,i);
Ans. 4
Q5. FILE *fp1,*fp2;
fp1=fopen("one","w")
fp2=fopen("one","w")
fputc('A',fp1)
fputc('B',fp2)
fclose(fp1)
fclose(fp2)
}
Find the Error, If Any?
Ans. no error. But It will over writes on same file.
What are the output(s) for the following ?
Q6. #include<malloc.h>
char *f()
{char *s=malloc(8);
strcpy(s,"goodbye");
}
main()
{
char *f();
printf("%c",*f()='A');
}
Q7. #define MAN(x,y) (x)>(y)?(x):(y)
{int i=10;
j=5;
k=0;
k=MAX(i++,++j);
printf(%d %d %d %d,i,j,k);
}
Ans. 10 5 0
Q8. a=10;
b=5; c=3;
d=3;
if(a<b)&&(c=d++)
printf(%d %d %d %d a,b,c,d);
else
printf("%d %d %d %d a,b,c,d);
Q9. #include<stdarg.h>
show(int t,va_list ptr1)
{
int a,x,i;
a=va_arg(ptr1,int);
printf("\n %d",a);
}
display(char)
{
int x;
listptr;
va_star(otr,s);
n=va_arg(ptr,int);
show(x,ptr);
}
main()
{
display("hello",4,12,13,14,44);
}
Q10. main()
{
printf("hello");
fork();
}
Q11. main()
{
int i = 10;
printf(" %d %d %d \n", ++i, i++, ++i);
}
Q12. #include<stdio.h>
main()
{
int *p, *c,i;
i = 5;
p = (int*) (malloc(sizeof(i)));
printf("\n%d",*p);
*p = 10;
printf("\n%d %d",i,*p);
c = (int*) calloc(2);
printf("\n%d\n",*c);
}
Q13. #define MAX(x,y) (x) >(y)?(x):(y)
main()
{
int i=10,j=5,k=0;
k= MAX(i++,++j);
printf("%d..%d..%d",i,j,k);
}
Q14.#include <stdio.h>
main()
{
enum _tag{ left=10, right, front=100, back};
printf("left is %d, right is %d, front is
%d, back is %d",left,right,front,back);
}
Q15. main()
{
int a=10,b=20;
a>=5?b=100:b=200;
printf("%d\n",b);
}
Q16.#define PRINT(int) printf("int = %d ",int)
main()
{
int x,y,z;
x=03;y=02;z=01;
PRINT(x^x);
z<<=3;
PRINT(x);
y>>=3;
PRINT(y);
}
Q17. #include<stdio.h>
main()
{
char s[] = "Bouquets and Brickbats";
printf("\n%c, ",*(&s[2]));
printf("%s, ",s+5);
printf("\n%s",s);
printf("\n%c",*(s+2));
}
Q18. main()
{
struct s1
{
char *str;
struct s1 *ptr;
};
static struct s1 arr[] = {
{"Hyderabad",arr+1},
{"Bangalore",arr+2},
{"Delhi",arr}
};
struct s1 *p[3];
int i;
for(i=0;i<=2;i++)
p[i] = arr[i].ptr;
printf("%s\n",(*p)->str);
printf("%s\n",(++*p)->str);
printf("%s\n",((*p)++)->str); }
Q19. .main()
{
char *p = "hello world!";
p[0] = 'H';
printf("%s",p);
}
func(int *i, int*j)
{*i=*i * *i;
*j=*j* *j;
}
main()
{ int i = 5, j = 2;
func(&i,&j);
printf("%d %d", i, j);}
What is the output?
void f(char *p)
{p=(char *) malloc(6);
strcpy(p,"hello");
}
void main( )
{char *P="bye";
f(p);
printf("%s',p);
}
For the following C program
int x(char *a)
{a=(char *) malloc(10*sizeof(char));
*a="hello";
}
main()
{char *a="new";
x(a);
printf("%s",a);
}
The output is
a) Hello
b) New
c) Hello new
d) Run time error
void main()
{
int d=5;
printf("%f",d);
}
Ans: Undefined
2.
void main()
{
int i;
for(i=1;i<4,i++)
switch(i)
case 1: printf("%d",i);break;
{
case 2:printf("%d",i);break;
case 3:printf("%d",i);break;
}
switch(i) case 4:printf("%d",i);
}
Ans: 1,2,3,4
3.
void main()
{
char *s="\12345s\n";
printf("%d",sizeof(s));
}
Ans: 6
4.
void main()
{
unsigned i=1; /* unsigned char k= -1 => k=255; */
signed j=-1; /* char k= -1 => k=65535 */
/* unsigned or signed int k= -1 =>k=65535 */
if(i<j)
printf("less");
else
if(i>j)
printf("greater");
else
if(i==j)
printf("equal");
}
Ans: less
5.
void main()
{
float j;
j=1000*1000;
printf("%f",j);
}
1. 1000000
2. Overflow
3. Error
4. None
Ans: 4
6. How do you declare an array of N pointers to functions returning
pointers to functions returning pointers to characters?
Ans: The first part of this question can be answered in at least
three ways:
1. char *(*(*a[N])())();
2. Build the declaration up incrementally, using typedefs:
typedef char *pc;
/* pointer to char */
typedef pc fpc();
/* function returning pointer to char */
typedef fpc *pfpc;
/* pointer to above */
typedef pfpc fpfpc();
/* function returning... */
typedef fpfpc *pfpfpc;
/* pointer to... */
pfpfpc a[N];
/* array of... */
3. Use the cdecl program, which turns English into C and
vice
versa:
cdecl> declare a as array of
pointer to function returning
pointer
to function returning pointer to char
char *(*(*a[])())()
cdecl can also explain complicated declarations, help
with
casts, and indicate which set of parentheses the arguments
go in (for complicated function definitions, like the
one
above).
Any good book on C should explain how to read these complicated
C declarations "inside out" to understand them ("declaration
mimics use").
The pointer-to-function declarations in the examples above
have
not included parameter type information. When the parameters
have complicated types, declarations can *really* get
messy.
(Modern versions of cdecl can help here, too.)
7. A structure pointer is defined of the type time . With 3 fields min,sec
hours having pointers to intergers.
Write the way to initialize the 2nd element to 10.
8. In the above question an array of pointers is declared.
Write the statement to initialize the 3rd element of the
2 element to 10;
9.
int f()
void main()
{
f(1);
f(1,2);
f(1,2,3);
}
f(int i,int j,int k)
{
printf("%d %d %d",i,j,k);
}
What are the number of syntax errors in the above?
Ans: None.
10.
void main()
{
int i=7;
printf("%d",i++*i++);
}
Ans: 56
11.
#define one 0
#ifdef one
printf("one is defined ");
#ifndef one
printf("one is not defined ");
Ans: "one is defined"
12.
void main()
{
int count=10,*temp,sum=0;
temp=&count;
*temp=20;
temp=∑
*temp=count;
printf("%d %d %d ",count,*temp,sum);
}
Ans: 20 20 20
13. There was question in c working only on unix machine with pattern matching.
14. what is alloca()
Ans : It allocates and frees memory after use/after getting out of scope
15.
main()
{
static i=3;
printf("%d",i--);
return i>0 ? main():0;
}
Ans: 321
16.
char *foo()
{
char result[100]);
strcpy(result,"anything is good");
return(result);
}
void main()
{
char *j;
j=foo()
printf("%s",j);
}
Ans: anything is good.
17.
void main()
{
char *s[]={ "dharma","hewlett-packard","siemens","ibm"};
char **p;
p=s;
printf("%s",++*p);
printf("%s",*p++);
printf("%s",++*p);
}
Ans: "harma" (p->add(dharma) && (*p)->harma)
"harma" (after printing, p->add(hewlett-packard) &&(*p)->harma)
"ewlett-packard"
For the following C program
#define AND &&
#define ARRANGE (a>25 AND a<50)
main()
{int a = 30;
if (ARRANGE)
printf("within range");
else
printf("out of range");
}
What is the output?
7. For the following C program
#define AREA(x)(3.14*x*x)
main()
{float r1=6.25,r2=2.5,a;
a=AREA(r1);
printf("\n Area of the circle is %f", a);
a=AREA(r2);
printf("\n Area of the circle is %f", a);
}
What is the output?
Ans. Area of the circle is 122.656250
Area of the circle is 19.625000
8. What do the following statements indicate. Explain.
*
int(*p)[10]
*
int*f()
*
int(*pf)()
*
int*p[10]
What is the mistake in the following program segment ?
f()
{
int a;
void c;
f2(&c,&a);}
2. a=0;
b=(a=0)?2:3;
a) What will be the value of b and why ?
b) If in first statement a=0 is replaced by a = -1, b= ?
c) If in second statement a=0 is replaced by a = -1, b=?
3. char *a[2];
int const *p;
int *const p;
struct new { int a;int b; *var[5] (struct new)}
Describe the statements in the above given construct ?
4. f()
{
int a=2;
f1(a++);
}
f1(int c)
{
printf("%d", c);
}
What is the value of c ?
5. f1()
{
f(3);
}
f(int t)
{
switch(t);
{
case 2: c=3;
case 3: c=4;
case 4: c=5;
case 5: c=6;
default: c=0;
}
What is the value of c?
6. What is the fallacy in the following program segment ?
int *f1()
{
int a=5;
return &a;
}
f()
int *b=f1()
int c=*b;
}
7. Give the C language equivalents of the following
a)Function returning an int pointer
b)Function pointer returning an int pointer
c)Function pointer returning an array of integers
d)Array of function pointer returning an array of integers
8. Find the fallacy in the following program segment?
int a;
short b;
b=a;
9. Define function ? Explain arguments in functions ?
10. How does C pass variables to a function ?
11. Explain the following program segment.
f(){
int *b;
*b=2;
}
12. Explain binary trees and their use ?
13. Draw the diagram showing the function stack, illustrating the variables
that were pushed on the stack at the point when
function f2 has been introduced .
type def struct
{ double x,double y} point; }
main( int argc, char *arg[3])
{ double a;
int b,c;
f1(a,b); }
f1(double x, int y)
{point p;
stack int n;
f2(p,x,y)
}
f2(point p, double angle)
{ int i,j,k,int max;
}
1. Declarations and Initializations
1.1 How do you decide which integer type to use?
1.4 What should the 64-bit type on new, 64-bit machines
be?
1.7 What's the best way to declare and define global variables?
1.11 What does extern mean in a function declaration?
1.12 What's the auto keyword good for?
1.14 I can't seem to define a linked list node which
contains a pointer to itself.
1.21 How do I declare an array of N pointers to functions
returning pointers to functions returning pointers to characters?
1.22 How can I declare a function that returns a pointer
to a function of its own type?
1.25 My compiler is complaining about an invalid redeclaration
of a function, but I only define it once and call it once.
1.30 What can I safely assume about the initial values
of variables which are not explicitly initialized?
1.31 Why can't I initialize a local array with a string?
1.32 What is the difference between char a[] = "string";
and char *p = "string"; ?
1.34 How do I initialize a pointer to a function?
2. Structures, Unions, and Enumerations
2.1 What's the difference between struct x1 { ...
}; and typedef struct { ... } x2; ?
2.2 Why doesn't "struct x { ... }; x thestruct;
"
work?
2.3 Can a structure contain a pointer to itself?
2.4 What's the best way of implementing opaque (abstract)
data types in C?
2.6 I came across some code that declared a structure with
the last member an array of one element, and then did some tricky allocation
to make it act like the array had several elements. Is this legal or portable?
2.7 I heard that structures could be assigned to variables
and passed to and from functions, but K&R1 says not.
2.8 Why can't you compare structures?
2.9 How are structure passing and returning implemented?
2.10 Can I pass constant values to functions which accept
structure arguments?
2.11 How can I read/write structures from/to data files?
2.12 How can I turn off structure padding?
2.13 Why does sizeof report a larger size than
I expect for a structure type?
2.14 How can I determine the byte offset of a field within
a structure?
2.15 How can I access structure fields by name at run
time?
2.18 I have a program which works correctly, but dumps
core after it finishes. Why?
2.20 Can I initialize unions?
2.22 What is the difference between an enumeration and
a set of preprocessor #defines?
2.24 Is there an easy way to print enumeration values
symbolically?
3. Expressions
3.1 Why doesn't the code "a[i] = i++;
" work?
3.2 Under my compiler, the code "int i = 7; printf("%d\n",
i++ * i++);
" prints 49. Regardless of the order of evaluation, shouldn't
it print 56?
3.3 How could the code [CENSORED] ever give 7?
3.4 Don't precedence and parentheses dictate order of
evaluation?
3.5 But what about the && and ||
operators?
3.8 What's a ``sequence point''?
3.9 So given "a[i] = i++;
" we don't know which
cell of a[] gets written to, but i does get incremented
by one.
3.12 If I'm not using the value of the expression, should
I use i++ or ++i to increment a variable?
3.14 Why doesn't the code "int a = 1000, b = 1000;
long int c = a * b;
" work?
3.16 Can I use ?: on the left-hand side of an
assignment expression?
4. Pointers
4.2 What's wrong with "char *p; *p = malloc(10);
"?
4.3 Does *p++ increment p, or what it
points to?
4.5 I want to use a char * pointer to step over
some ints. Why doesn't "((int *)p)++;
" work?
4.8 I have a function which accepts, and is supposed to
initialize, a pointer, but the pointer in the caller remains unchanged.
4.9 Can I use a void ** pointer to pass a generic
pointer to a function by reference?
4.10 I have a function which accepts a pointer to an int.
How can I pass a constant like 5 to it?
4.11 Does C even have ``pass by reference''?
4.12 I've seen different methods used for calling functions
via pointers.
5. Null Pointers
5.1 What is this infamous null pointer, anyway?
5.2 How do I get a null pointer in my programs?
5.3 Is the abbreviated pointer comparison ``if(p)''
to test for non-null pointers valid?
5.4 What is NULL and how is it #defined?
5.5 How should NULL be defined on a machine which
uses a nonzero bit pattern as the internal representation of a null pointer?
5.6 If NULL were defined as ``((char *)0),''
wouldn't that make function calls which pass an uncast NULL work?
5.9 If NULL and 0 are equivalent as
null pointer constants, which should I use?
5.10 But wouldn't it be better to use NULL, in
case the value of NULL changes?
5.12 I use the preprocessor macro "#define Nullptr(type)
(type *)0
" to help me build null pointers of the correct type.
5.13 This is strange. NULL is guaranteed to be
0, but the null pointer is not?
5.14 Why is there so much confusion surrounding null pointers?
5.15 I'm confused. I just can't understand all this null
pointer stuff.
5.16 Given all the confusion surrounding null pointers,
wouldn't it be easier simply to require them to be represented internally
by zeroes?
5.17 Seriously, have any actual machines really used nonzero
null pointers?
5.20 What does a run-time ``null pointer assignment''
error mean?
6. Arrays and Pointers
6.1 I had the definition char a[6] in one source
file, and in another I declared extern char *a. Why didn't it work?
6.2 But I heard that char a[] was identical to
char *a.
6.3 So what is meant by the ``equivalence of pointers
and arrays'' in C?
6.4 Why are array and pointer declarations interchangeable
as function formal parameters?
6.7 How can an array be an lvalue, if you can't assign
to it?
6.8 What is the real difference between arrays and pointers?
6.9 Someone explained to me that arrays were really just
constant pointers.
6.11 I came across some ``joke'' code containing the
``expression'' 5["abcdef"] . How can this be legal C?
6.12 What's the difference between array and
&array?
6.13 How do I declare a pointer to an array?
6.14 How can I set an array's size at compile time?
6.15 How can I declare local arrays of a size matching
a passed-in array?
6.16 How can I dynamically allocate a multidimensional
array?
6.17 Can I simulate a non-0-based array with a pointer?
6.18 My compiler complained when I passed a two-dimensional
array to a function expecting a pointer to a pointer.
6.19 How do I write functions which accept two-dimensional
arrays when the ``width'' is not known at compile time?
6.20 How can I use statically- and dynamically-allocated
multidimensional arrays interchangeably when passing them to functions?
6.21 Why doesn't sizeof properly report the size
of an array which is a parameter to a function?
7. Memory Allocation
7.1 Why doesn't the code ``char *answer; gets(answer);''
work?
7.2 I can't get strcat to work. I tried ``char
*s3 = strcat(s1, s2);'' but I got strange results.
7.3 But the man page for strcat says that it
takes two char *'s as arguments. How am I supposed to know to allocate
things?
7.5 I have a function that is supposed to return a string,
but when it returns to its caller, the returned string is garbage.
7.6 Why am I getting ``warning: assignment of pointer
from integer lacks a cast'' for calls to malloc?
7.7 Why does some code carefully cast the values returned
by malloc to the pointer type being allocated?
7.8 Why does so much code leave out the multiplication
by sizeof(char) when allocating strings?
7.14 I've heard that some operating systems don't actually
allocate malloc'ed memory until the program tries to use it. Is
this legal?
7.16 I'm allocating a large array for some numeric work,
but malloc is acting strangely.
7.17 I've got 8 meg of memory in my PC. Why can I only
seem to malloc 640K or so?
7.19 My program is crashing, apparently somewhere down
inside malloc.
7.20 You can't use dynamically-allocated memory after
you free it, can you?
7.21 Why isn't a pointer null after calling free?
7.22 When I call malloc to allocate memory for
a local pointer, do I have to explicitly free it?
7.23 When I free a dynamically-allocated structure containing
pointers, do I have to free each subsidiary pointer first?
7.24 Must I free allocated memory before the program exits?
7.25 Why doesn't my program's memory usage go down when
I free memory?
7.26 How does free know how many bytes to free?
7.27 So can I query the malloc package to find out how
big an allocated block is?
7.30 Is it legal to pass a null pointer as the first argument
to realloc?
7.31 What's the difference between calloc and
malloc?
7.32 What is alloca and why is its use discouraged?
8. Characters and Strings
8.1 Why doesn't "strcat(string, '!');
" work?
8.2 Why won't the test if(string == "value") correctly
compare string against the value?
8.3 Why can't I assign strings to character arrays?
8.6 How can I get the numeric (character set) value corresponding
to a character?
8.9 Why is sizeof('a') not 1?
9. Boolean Expressions and Variables
9.1 What is the right type to use for Boolean values in
C?
9.2 What if a built-in logical or relational operator
``returns'' something other than 1?
9.3 Is if(p), where p is a pointer, valid?
10. C Preprocessor
10.2 I've got some cute preprocessor macros that let me
write C code that looks more like Pascal. What do y'all think?
10.3 How can I write a generic macro to swap two values?
10.4 What's the best way to write a multi-statement macro?
10.6 What are .h files and what should I put in them?
10.7 Is it acceptable for one header file to #include
another?
10.8 Where are header (``#include'') files searched
for?
10.9 I'm getting strange syntax errors on the very first
declaration in a file, but it looks fine.
10.11 Where can I get a copy of a missing header file?
10.12 How can I construct preprocessor #if expressions
which compare strings?
10.13 Does the sizeof operator work in preprocessor
#if directives?
10.14 Can I use an #ifdef in a #define
line, to define something two different ways?
10.15 Is there anything like an #ifdef for
typedefs?
10.16 How can I use a preprocessor #if expression
to detect endianness?
10.18 How can I preprocess some code to remove selected
conditional compilations, without preprocessing everything?
10.19 How can I list all of the pre#defined identifiers?
10.20 I have some old code that tries to construct identifiers
with a macro like "#define Paste(a, b) a/**/b
", but it doesn't
work any more.
10.22
What does the message ``warning: macro replacement within a string literal''
mean?
10.23 How can I use a macro argument inside a string literal
in the macro expansion?
10.25 I've got this tricky preprocessing I want to do and
I can't figure out a way to do it.
10.26 How can I write a macro which takes a variable number
of arguments?
11. ANSI/ISO Standard C
11.1 What is the ``ANSI C Standard?''
11.2 How can I get a copy of the Standard?
11.3 My ANSI compiler is complaining about prototype mismatches
for parameters declared float.
11.4 Can you mix old-style and new-style function syntax?
11.5 Why does the declaration "extern f(struct x
*p);
" give me a warning message?
11.8 Why can't I use const values in initializers
and array dimensions?
11.9 What's the difference between const char *p
and char * const p?
11.10 Why can't I pass a char ** to a function
which expects a const char **?
11.12 Can I declare main as void, to
shut off these annoying ``main returns no value'' messages?
11.13 But what about main's third argument, envp?
11.14 I believe that declaring void main() can't
fail, since I'm calling exit instead of returning.
11.15 The book I've been using always uses void main().
11.16 Is exit(status) truly equivalent to returning
the same status from main?
11.17 How do I get the ANSI ``stringizing'' preprocessing
operator `#' to stringize the macro's value instead of its name?
11.18 What does the message ``warning: macro replacement
within a string literal'' mean?
11.19 I'm getting strange syntax errors inside lines I've
#ifdeffed out.
11.20 What are #pragmas ?
11.21 What does ``#pragma once'' mean?
11.22 Is char a[3] = "abc"; legal?
11.24 Why can't I perform arithmetic on a void *
pointer?
11.25 What's the difference between memcpy and
memmove?
11.26 What should malloc(0) do?
11.27 Why does the ANSI Standard not guarantee more than
six case-insensitive characters of external identifier significance?
11.29 My compiler is rejecting the simplest possible test
programs, with all kinds of syntax errors.
11.30 Why are some ANSI/ISO Standard library routines
showing up as undefined, even though I've got an ANSI compiler?
11.31 Does anyone have a tool for converting old-style
C programs to ANSI C, or for automatically generating prototypes?
11.32 Why won't frobozz-cc, which claims to be ANSI compliant,
accept this code?
11.33 What's the difference between implementation-defined,
unspecified, and undefined behavior?
11.34 I'm appalled that the ANSI Standard leaves so many
issues undefined.
11.35 I just tried some allegedly-undefined code on an
ANSI-conforming compiler, and got the results I expected.
12. Stdio
12.1 What's wrong with the code "char c; while((c
= getchar()) != EOF) ...
"?
12.2 Why won't the code `` while(!feof(infp)) { fgets(buf,
MAXLINE, infp); fputs(buf, outfp); } '' work?
12.4 My program's prompts and intermediate output don't
always show up on the screen.
12.5 How can I read one character at a time, without
waiting for the RETURN key?
12.6 How can I print a '%' character with printf?
12.9 How can printf use %f for type
double, if scanf requires %lf?
12.10 How can I implement a variable field width with
printf?
12.11 How can I print numbers with commas separating the
thousands?
12.12 Why doesn't the call scanf("%d", i) work?
12.13 Why doesn't the code "double d; scanf("%f",
&d);
" work?
12.15 How can I specify a variable width in a scanf
format string?
12.17 When I read numbers from the keyboard with scanf
"%d\n", it seems to hang until I type one extra line of input.
12.18 I'm reading a number with scanf %d
and then a string with gets(), but the compiler seems to be skipping
the call to gets()!
12.19 I'm re-prompting the user if scanf fails,
but sometimes it seems to go into an infinite loop.
12.20 Why does everyone say not to use scanf?
What should I use instead?
12.21 How can I tell how much destination buffer space
I'll need for an arbitrary sprintf call? How can I avoid overflowing
the destination buffer with sprintf?
12.23 Why does everyone say not to use gets()?
12.24 Why does errno contain ENOTTY after a call
to printf?
12.25 What's the difference between fgetpos/fsetpos
and ftell/fseek?
12.26 Will fflush(stdin) flush unread characters
from the standard input stream?
12.30 I'm trying to update a file in place, by using fopen
mode "r+", but it's not working.
12.33 How can I redirect stdin or stdout
from within a program?
12.34 Once I've used freopen, how can I get the
original stream back?
12.38 How can I read a binary data file properly?
13. Library Functions
13.1 How can I convert numbers to strings?
13.2 Why does strncpy not always write a '\0'?
13.5 Why do some versions of toupper act strangely
if given an upper-case letter?
13.6 How can I split up a string into whitespace-separated
fields?
13.7 I need some code to do regular expression and wildcard
matching.
13.8 I'm trying to sort an array of strings with qsort,
using strcmp as the comparison function, but it's not working.
13.9 Now I'm trying to sort an array of structures, but
the compiler is complaining that the function is of the wrong type for qsort.
13.10 How can I sort a linked list?
13.11 How can I sort more data than will fit in memory?
13.12 How can I get the time of day in a C program?
13.13 How can I convert a struct tm or a string
into a time_t?
13.14 How can I perform calendar manipulations?
13.15 I need a random number generator.
13.16 How can I get random integers in a certain range?
13.17 Each time I run my program, I get the same sequence
of numbers back from rand().
13.18 I need a random true/false value, so I'm just taking
rand() % 2, but it's alternating 0, 1, 0, 1, 0...
13.20 How can I generate random numbers with a normal
or Gaussian distribution?
13.24 I'm trying to port this old program. Why do I get
``undefined external'' errors for some library functions?
13.25 I get errors due to library functions being undefined
even though I #include the right header files.
13.26 I'm still getting errors due to library functions
being undefined, even though I'm requesting the right libraries.
13.28 What does it mean when the linker says that _end
is undefined?
14. Floating Point
14.1 When I set a float variable to 3.1, why
is printf printing it as 3.0999999?
14.2 Why is sqrt(144.) giving me crazy numbers?
14.3 I keep getting ``undefined: sin'' compilation errors.
14.4 My floating-point calculations are acting strangely
and giving me different answers on different machines.
14.5 What's a good way to check for ``close enough'' floating-point
equality?
14.6 How do I round numbers?
14.7 Where is C's exponentiation operator?
14.8 The pre-#defined constant M_PI seems
to be missing from <math.h>.
14.9 How do I test for IEEE NaN and other special values?
14.11 What's a good way to implement complex numbers in
C?
14.12 I'm looking for some mathematical library code.
14.13 I'm having trouble with a Turbo C program which
crashes and says something like ``floating point formats not linked.''
15. Variable-Length Argument Lists
15.1 I heard that you have to #include <stdio.h>
before calling printf. Why?
15.2 How can %f be used for both float
and double arguments in printf?
15.3 Why don't function prototypes guard against mismatches
in printf's arguments?
15.4 How can I write a function that takes a variable
number of arguments?
15.5 How can I write a function that takes a format string
and a variable number of arguments, like printf, and passes them
to printf to do most of the work?
15.6 How can I write a function analogous to scanf,
that calls scanf to do most of the work?
15.7 I have a pre-ANSI compiler, without <stdarg.h>.
What can I do?
15.8 How can I discover how many arguments a function
was actually called with?
15.9 My compiler isn't letting me declare a function that
accepts only variable arguments.
15.10 Why isn't "va_arg(argp, float)
" working?
15.11 I can't get va_arg to pull in an argument
of type pointer-to-function.
15.12 How can I write a function which takes a variable
number of arguments and passes them to some other function ?
15.13 How can I call a function with an argument list
built up at run time?
16. Strange Problems
16.3 This program crashes before it even runs!
16.4 I have a program that seems to run correctly, but
then crashes as it's exiting.
16.5 This program runs perfectly on one machine, but I
get weird results on another.
16.6 Why does the code "char *p = "hello, world!";
p[0] = 'H';
" crash?
16.8 What does ``Segmentation violation'' mean?
17. Style
17.1 What's the best style for code layout in C?
17.3 Is the code "if(!strcmp(s1, s2))
" good
style?
17.4 Why do some people write if(0 == x) instead
of if(x == 0)?
17.5 I came across some code that puts a (void)
cast before each call to printf. Why?
17.8 What is Hungarian Notation''? Is it worthwhile?
17.9 Where can I get the ``Indian Hill Style Guide'' and
other coding standards?
17.10 Some people say that goto's are evil and
that I should never use them. Isn't that a bit extreme?
18. Tools and Resources
18.1 I'm looking for C development tools (cross-reference
generators, code beautifiers, etc.).
18.2 How can I track down these pesky malloc problems?
18.3 What's a free or cheap C compiler I can use?
18.4 I just typed in this program, and it's acting
strangely. Can you see anything wrong with it?
18.5 How can I shut off the ``warning: possible pointer
alignment problem'' message which lint gives me for each call to
malloc?
18.7 Where can I get an ANSI-compatible lint?
18.8 Don't ANSI function prototypes render lint
obsolete?
18.9 Are there any C tutorials or other resources on the
net?
18.10 What's a good book for learning C?
18.13 Where can I find the sources of the standard C libraries?
18.14 I need code to parse and evaluate expressions.
18.15 Where can I get a BNF or YACC grammar for C?
18.15a Does anyone have a C compiler test suite I can
use?
18.16 Where and how can I get copies of all these freely
distributable programs?
19. System Dependencies
19.1 How can I read a single character from the keyboard
without waiting for the RETURN key?
19.2 How can I find out how many characters are available
for reading, or do a non-blocking read?
19.3 How can I display a percentage-done indication that
updates itself in place, or show one of those ``twirling baton'' progress
indicators?
19.4 How can I clear the screen, or print things in inverse
video, or move the cursor?
19.5 How do I read the arrow keys? What about function
keys?
19.6 How do I read the mouse?
19.7 How can I do serial (``comm'') port I/O?
19.8 How can I direct output to the printer?
19.9 How do I send escape sequences to control a terminal
or other device?
19.10 How can I do graphics?
19.11 How can I check whether a file exists?
19.12 How can I find out the size of a file, prior to
reading it in?
19.13 How can a file be shortened in-place without completely
clearing or rewriting it?
19.14 How can I insert or delete a line in the middle
of a file?
19.15 How can I recover the file name given an open file
descriptor?
19.16 How can I delete a file?
19.17 What's wrong with the call "fopen("c:\newdir\file.dat",
"r")
"?
19.18 How can I increase the allowable number of simultaneously
open files?
19.20 How can I read a directory in a C program?
19.22 How can I find out how much memory is available?
19.23 How can I allocate arrays or structures bigger than
64K?
19.24 What does the error message ``DGROUP exceeds 64K''
mean?
19.25 How can I access memory located at a certain address?
19.27 How can I invoke another program from within a C
program?
19.30 How can I invoke another program and trap its output?
19.31 How can my program discover the complete pathname
to the executable from which it was invoked?
19.32 How can I automatically locate a program's configuration
files in the same directory as the executable?
19.33 How can a process change an environment variable
in its caller?
19.36 How can I read in an object file and jump to routines
in it?
19.37 How can I implement a delay, or time a user's response,
with sub-second resolution?
19.38 How can I trap or ignore keyboard interrupts like
control-C?
19.39 How can I handle floating-point exceptions gracefully?
19.40 How do I... Use sockets? Do networking? Write client/server
applications?
19.40b How do I use BIOS calls? How can I write ISR's?
How can I create TSR's?
19.41 But I can't use all these nonstandard, system-dependent
functions, because my program has to be ANSI compatible!
20. Miscellaneous
20.1 How can I return multiple values from a function?
20.3 How do I access command-line arguments?
20.5 How can I write data files which can be read on other
machines with different data formats?
20.6 How can I call a function, given its name as a string?
20.8 How can I implement sets or arrays of bits?
20.9 How can I determine whether a machine's byte order
is big-endian or little-endian?
20.10 How can I convert integers to binary or hexadecimal?
20.11 Can I use base-2 constants (something like 0b101010)?
Is there a printf format for binary?
20.12 What is the most efficient way to count the number
of bits which are set in a value?
20.13 How can I make my code more efficient?
20.14 Are pointers really faster than arrays? How much
do function calls slow things down?
20.17 Is there a way to switch on strings?
20.18 Is there a way to have non-constant case
labels (i.e. ranges or arbitrary expressions)?
20.19 Are the outer parentheses in return statements
really optional?
20.20 Why don't C comments nest? Are they legal inside
quoted strings?
20.24 Why doesn't C have nested functions?
20.25 How can I call FORTRAN (C++, BASIC, Pascal, Ada,
LISP) functions from C?
20.26 Does anyone know of a program for converting Pascal
or FORTRAN to C?
20.27 Can I use a C++ compiler to compile C code?
20.28 I need to compare two strings for close, but not
necessarily exact, equality.
20.29 What is hashing?
20.31 How can I find the day of the week given the date?
20.32 Will 2000 be a leap year?
20.34 How do you write a program which produces its own
source code as its output?
20.35 What is ``Duff's Device''?
20.36 When will the next Obfuscated C Code Contest be
held? How can I get a copy of previous winning entries?
20.37 What was the entry keyword mentioned in
K&R1?
20.38 Where does the name ``C'' come from, anyway?
20.39 How do you pronounce ``char''?
20.40 Where can I get extra copies of this list?
top