Short Jump (SJMP) Instruction for Assembly Language Programming

Jumping Around with SJMP in Assembly Language

The SJMP (short jump) instruction allows program code to move from one point in a program to another without having to execute all the instructions in between. It may be used to create a loop, change the flow of execution, or perform other functions. In this tutorial, we will look at how to use SJMP in assembly language.

Using SJMP

At its simplest, an SJMP instruction is written as follows:

SJMP label

Where “label” is the name of the code section you want to jump to. This works much like a GOTO statement in higher-level languages, allowing you to jump anywhere in the code. The difference here is that the jump can only take place within the same code segment, which limits its usefulness somewhat.

Another way to use SJMP is to create a loop structure. This works by creating a label at the start of the code section you want to loop back to and then adding an SJMP instruction right before the end of the loop. For example:

  START_LOOP:
        ; Body of the loop code goes here...
        SJMP START_LOOP
  END_LOOP: ; End of the loop code

This will cause the code to loop back to the beginning each time it reaches the end, effectively creating a loop. This type of looping structure is extremely common in assembly language programming.

Conclusion

The SJMP instruction is a powerful and versatile tool for controlling program flow in assembly language. It can be used for looping, branching, and performing other tasks. With just a few lines of code, you can create powerful control structures that make your programs more efficient and easier to read.