Created on 26.03.01
Source URL: http://www.oocities.org/maxspaceuk
Chapter II
Mathematical Calculations
QBasic was obviously created for us to have fun, play games, draw nice graphics and even make sounds.
But, as you might guess, nothing good comes without a bit of effort that has to be put in it. In the most QBasic programs a bit of math has to be done.
The math… Doh!
If you hate mathematics, don’t worry. Qbasic will do it all for you, you just need to know how to tell QBasic to do that.
Qbasic can perform the following mathematical operations:
Operator | What it does | Example | Result |
+ | Add | 7 + 2 | 9 |
- | Subtract | 7 – 2 | 5 |
* | Multiply | 7 * 2 | 14 |
/ | Divide | 7 / 2 | 3.5 |
Examples:
1. a = 15 / 4 + 3
PRINT a
Result on the screen – 6
2. PRINT “Enter the first number”
INPUT a
PRINT “Enter the second number”
INPUT b
c = a + b
d = a * b
PRINT a; “+”; b; “=”; c
PRINT a; “*”; b; “=”; d
END
When you run this program it goes like this:
Computer: Enter the first number
You: 22
Computer: Enter the second number
You: 18
Computer: 22 + 18 = 40
22 * 18 = 396
Advanced operations:
Operator | What it does | Example | Result |
\ | divides and turns the result into an integer (the whole number) | 7 \ 2 | 3 |
^ | Raises a number to the power of another number | 3 ^ 4 (means: 3 * 3 * 3 * 3) 2.5 ^ 3 (means:2.5 * 2.5 * 2.5) | 243 15.625 |
SQR | Calculates the square root of a number | SQR(9) SQR(16) SQR(5) | 3 (because: 3 ^ 2 = 9) 4 (because: 4 ^ 2 = 16) 2.236 |
MOD | Divides two numbers, and if the result is not an integer (for example - 3.25), finds out how much to subtract from the first number in order to get the integer result. | 17 MOD 5 | 2 (because: 17 / 5 = 3.4 17 – 2 = 15 15 / 5 = 3) |
The following program explains MOD. Type this program (except my comments) into Qbasic accurately and run it to see how MOD works.
1 CLS this command clears the screen, so it’s empty
INPUT "Enter the first number "; a
INPUT "Enter the second number "; b
IF b = 0 THEN checks if the second number is zero, because you can’t divide by zero
PRINT "the second number cannot be 0. Try again."
DO: LOOP WHILE INKEY$ = "" waits for you to press a key to continue
GOTO 1 then sends you back to line 1
END IF
CLS clear the screen again
c = a MOD b
d = a / b
e = a - c
f = e / b
PRINT a; "MOD"; b; "="; c
IF c = 0 THEN this checks if the result of a MOD b = 0, because it means that
the result of a / b is integer
PRINT "because"; a; "/"; b; "="; d; " - integer. Try again."
DO: LOOP WHILE INKEY$ = "" waits for you to press a key to continue
GOTO 1 then sends you back to the line 1
END IF
PRINT "because"; a; "/"; b; "="; d; " -not integer" The rest of the program executes if the
PRINT "but"; a; "-"; c; "="; e result of a / b is not integer
PRINT "and"; e; "/"; b; "="; f; " - integer"
END
This program may look very complicated for you, but don’t worry. Qbasic is a very easy language to learn and soon you’ll be having fun with it. I promise you!
To the next chapter = >
To the Top
BACK TO THE MAIN PAGE