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JMP  -  Jump Instruction


The JMP instruction is generally used to pass control to a routine, label or far address. Unlike CALL it does not return to the caller if a RET is reached.

The memory address of the destination is supplied in the operand.

Alternately the destination can a relative address stated as positive or negative count of bytes from the current instruction.

This command has 2 parts, Instruction, then either a Register, Immediate value, Label, Routine Name or a memory address.

The 8 bit near jumps can jump up to 127 bytes forward or backward. Forward start at 0h to 79h, backward start from FFh to 80h.

See also Condition Jumps.

Examples show how to call a sub routine at:
000007D4 SubPressAnyKey: is called with - JMP SubPressAnyKey

Assembly
Sample		 Description   16 bit Machine
  Code
JMP 0x03;  Jump forward using an 8 bit relative
;  number 		  EB 03
JMP 0xFD;  Jump backwards using an 8 bit
;  relative number 		  EB FD
JMP 0x07D4;  Jump forward using a 16 bit relative
;  number 		  E9 D4 07
JMP SubPressAnyKey;  Jump forward relative using
;  a Label or Routine name 		  E9 79 05
JMP AX;  Jump using an absolute 16 bit
;  register 		  FF E0
MOV BX, 0x0020;  Assign a memory location   BB 20 00
MOV [BX], 0x07D4;  Assign a valid sub routine address   C7 07 D4 07
JMP [BX];  Jump using a direct memory address   FF 27