assembly notes

assembly notes - DX[00[00 AX[07[E0 mov cx 7Eh mov ax 1000h...

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MUL instruction can use 1 byte 2 byte or 4 byte register/memloc multiplying 1 byte MUL CL ; put into AX = CL * AL goes into 2 byte register --- never overflow multiply a 2 byte MUL CX ; DX:AX = CX * AX split between 2 two-byte registers MUL ECX ; EDX:EAX =ECX * EAX - split between 2 four-byte registers examples mov cl, 7Eh mov al, 10h mul cl ; ax = 7Eh * 10h = 07E0h stored: AX:[07][E0] mov cx, 7Eh mov ax, 10h mul cx ;DX:AX = 7Eh * 10h = 07E0h stored:
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Unformatted text preview: DX:[00][00] AX:[07][E0] mov cx, 7Eh mov ax, 1000h mul cx ; DX:AX =7Eh * 1000h = 07E000h stored: DX:[00][07] AX:[E0][00] mov ecx, 7Eh mov eax, 1000h mul ecx ;EDX:EAX stored: edx:[00][00][00][00] eax: [00][07][E0][00] IMUL instruction same as MUL instruction plus some stuff: can do IMUL op ;multiplies "A" registers by op IMUL op1, op2 ;multiplies 1 and 2 stores in 1 IMUL op1,op2,op3 ; multiplies 2 and 3 and stores in 1...
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