Arithmetic Group

These instructions perform arithmetic operations such as addition, subtraction, increment, and decrement.

Addition

Any 8-bit number, or the contents of a register or the contents of a memory location can be added to the contents of the accumulator and the sum is stored in the accumulator. No two other 8-bit registers can be added directly (e.g., the contents of register B cannot be added directly to the contents of the register C). The instruction DAD is an exception; it adds 16-bit data directly in register pairs.

ADD           Add to Accumulator

ADI           Add Immediate Data to Accumulator

ADC           Add to Accumulator Using Carry Flag

ACI           Add Immediate data to Accumulator Using Carry 

Subtraction

Any 8-bit number, or the contents of a register, or the contents of a memory location can be subtracted from the contents of the accumulator and the results stored in the accumulator. The subtraction is performed in 2's compliment, and the results if negative, are expressed in 2's complement. No two other registers can be subtracted directly.

SUB           Subtract from Accumulator

SUI           Subtract Immediate Data from Accumulator

SBB           Subtract from Accumulator Using Borrow (Carry) Flag

SBI           Subtract Immediate from Accumulator Using Borrow (Carry) Flag

Increment/Decrement

The 8-bit contents of a register or a memory location can be incremented or decrement by 1. Similarly, the 16-bit contents of a register pair (such as BC) can be incremented or decrement by 1. These increment and decrement operations differ from addition and subtraction in an important way; i.e., they can be performed in any one of the registers or in a memory location.

INR           Increment Specified Byte by One

DCR           Decrement Specified Byte by One

INX           Increment Register Pair by One

DCX           Decrement Register Pair by One

DAD           Double Register Add; Add Content of Register

              Pair to H & L Register Pair

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