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The flag

The flag register is one of the special purpose register. The flag bits are changed to 0 or 1 depending upon the value of result after arithmetic or logical operations.

We can divide the flag bits into two sections. The Status Flags, and the Control Flags.

Control Flags

There are 3 different flags which are used to enable or disable some basic operations of the microprocessor. These flags and their functions are listed below.

General Purpose Registers 

There are six general-purpose registers to store 8-bit data; these are identified as- B, C, D, E, H, and L. These can be combined as register pairs – BC, DE, and HL, to perform some 16-bit operation. These registers are used to store or copy temporary data, by using instructions, during the execution of the program.

Specific Purpose Registers


The accumulator is an 8-bit register (can store 8-bit data) that is the part of the arithmetic and logical unit (ALU). After performing arithmetical or logical operations, the result is stored in accumulator. Accumulator is also defined as register A.

Memory Registers

There are two 16-bit registers used to hold memory addresses. The size of these registers is 16 bits because the memory addresses are 16 bits. They are :-

· Program Counter: This register is used to sequence the execution of the instructions. The function of the program counter is to point to the memory address from which the next byte is to be fetched. When a byte (machine code) is being fetched, the program counter is incremented by one to point to the next memory location.

· Stack Pointer: It is used as a memory pointer. It points to a memory location in read/write memory, called the stack. It is always incremented/decremented by 2 during push and pop operation.

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