"E97": example of branch program

Arbitrary integer numbers are stored in registers R1, R2 and R3. Find maximum of them and put it into R0.

At first we'll copy maximum of R1 and R2 to R0. Then, if R3>R0, it's necessary to replace R0 value by R3.

Address	Code	Operation	Comments
0000	0412	compare R2 and R1	compare R2 and R1
0002	3D04	if < 0, then pc=pc+4	to 0008
0004	0120	R2 ==> R0	remember R2
0006	1D02	pc=pc+2	to 000A - bypass second branch
0008	0110	R1 ==> R0	remember R1
000A	0403	compare R3 with R0	compare R3 with R0
000C	3D02	if < 0, then pc=pc+2	to 0010
000E	0130	R3 ==> R0	remember R3
0010	0F00	halt	stop

We can rewrite our program with jump instructions: it will become more demonstrative, but longer. It also will lose relocation properties - we will not be able to move it to anotther address without changes.

Try to input and check this variant of the program yourself.

Address	Code	Operation	Comments
0000	0412	compare R2 and R1
0002 0004	3C0D 000C	if < 0, then to 000C
0006	0120	R2 ==> R0	remember R2
0008 000A	1C0D 000E	jump to 000E	bypass second branch
000C	0110	R1 ==> R0	remember R1
000E	0403	compare R3 with R0
0010 0012	3C0D 0016	if < 0, then to 0016
0014	0130	R3 ==> R0	remember R3
0016	0F00	halt	stop

Try and examine, how it works in "E97". Don't forget to determine R1-R3 values before running a program.