30-10-2012, 04:01 PM
Data Transfer and Manipulation
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• There is a basic set of operations that most computers include in their instruction set
• The opcode and/or symbolic code may differ for the same instruction among different computers
• There are three main categories of computer instructions:
o Data transfer
o Data manipulation
o Program control
• Data transfer instructions: transfer data from one location to another without changing the binary information content
Load:------ ST Output OUT
Move ------MOV Push PUSH
Exchange --XCH Pop POP
• Some assembly language conventions modify the mnemonic symbol to differentiate between addressing modes eg LDI – load immediate
• Some use a special character to designate the mode
Program Control
• Program control instructions: provide decision-making capabilities and change the program path
• Typically, the program counter is incremented during the fetch phase to the location of the next instruction
• A program control type of instruction may change the address value in the program counter and cause the flow of control to be altered
• This provides control over the flow of program execution and a capability for branching to different program segments
• Branch BR
• Return RET
• Jump JMP
• Compare CMP
• Skip SKP
• Test TST
• Call CALL