created: 07/18/01; edits: 10/20/01, 02/22/03, 06/26/03, 07/06/15, 02/29/20, 10/07/21
created: 07/18/01; edits: 10/20/01, 02/22/03, 06/26/03, 07/06/15, 02/29/20, 10/07/21
The
power of computers
is their ability to repeat actions
and to alter their operation
depending on data.
Modern programming languages express
these abilities using control structures.
Repeated action (iteration) is done with a
while structure.
Alternative control paths (alternation) is done with an
if-then-else structure.
The machine instructions of the processor do not have these structures, nor does assembly language. In assembly language you must build these structures out of basic assembly instructions. These basic instructions are the jump instructions and the conditional branch instructions.
j instruction (jump)beq instruction (branch equal)bne instruction (branch not equal)When a program is executing, does each machine instruction have an address in main memory?