Question

What is flow control? Give two examples of instructions that are used to accomplish it.

Answer 1

We know that sequential statements are executed line by line i.e in a sequential manner.

flow control defines how the statements/instructions are executed . flow control keeps track of all instructions flow.

example:

mov ax,5

mov bx,5

jmp label1:

mov cx,3

label1:

.....

....

In the above example, mov instructions are executed normally but jmp instruction causes the change in program flow , control will go to label1: (it is called unconditional jump), rather than executing mov cx,3.

Two example instructions are:

JC----> jump if carry

this instruction will change the control flow of program when carry flag (CF) is set to 1

JA-----> jump if above

ex: cmp ax,bx

ja label2

...

label2:

....

It is used with unsigned (positive) numbers.

The above instruction changes the control flow if first operand value is greater than second operand.