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SHL  -  Shift Left Instruction


The SHL instruction is used to perform a logical shift left, resulting in a multiplication.

As each bit is shift it passes in to the Carry flag, where it can be assessed using a conditional jump JC or JNC.

As each bit moves left the lowest bit becomes zero.

This command has 3 part the Instruction, a Register or memory address, and the number of bits to shift left.

Assembly
Sample		 Description 16 bit Machine
Code
SHL AL, 1;  Shift AL left by 1 bit   D0 E0
SHL AL, CL;  Shift AL left by value of CL   D2 E0
SHL AL, 0x03 ;  Shift AL left by 8 bit immediate   C0 E0 03
SHL AX, 1;  Shift AL left by 1 bit   D1 E0
SHL AX, CL ;  Shift AL left by value of CL   D3 E0
SHL AX, 0x03 ;  Shift AL left by 8 bit immediate   C1 E0 03
SHL [BX], 1;  Shift memory address left by 1 bit   D1 27
SHL [BX], CL;  Shift memory address left by value of CL   D3 27
SHL [BX], 0x03 ;  Shift memory address left by 8 bit
;  immediate 		  C1 27 03
SHL [BX+2], 1;  Shift memory address left by 1 bit   D1 67 02
SHL [BX+2], CL ;  Shift memory address left by value of CL   D3 67 02
SHL [BX+2], 0x03 ;  Shift memory address left by 8 bit
;  immediate 		  C1 67 02 03