Register Assignment

NAMES : MWABA ANTHONY
ID NUMBER : DC – 2157
PROGRAME : COMPUTER STUDIES WITH EDUCATION
COURSE : COMPUTER ARCHITECTURE
LECTURE : MR. CHISHIMBA
ASSIGNMENT : ONE
TERM : ONE
DUE DATE : 24TH/2/21
TASK : REGISTERS
A register is a temporary storage area built into a Central Processing Unit (CPU). Some
registers are used internally and cannot be accessed outside the processor, while others are
user-accessible. Most modern CPU architectures include both types of registers according to
the website Techterms.com. This assignment will be describing registers in terms of name
and where they are found. These registers are the top of the memory hierarchy, and are the
fastest way for the system to manipulate data.
Registers are the most important components of CPU. There are various types of Registers
those are used for various purpose. In a very simple microprocessor, it consists of a single
memory location, usually called an accumulator. Some Mostly used Registers are
Accumulator (AC), Data Register (DR), Address Register (AR), Program Counter (PC),
Memory Data Register (MDR), Index Register (IR), and Memory Buffer Register (MBR).
Registers vary in both number and size, depending on the CPU architecture. Some processors
have 8 registers while others have 16, 32, or more. For many years, registers were 32-bit, but
now many are 64-bit in size. A 64-bit register is necessary for a 64-bit processor, since it
enables the CPU to access 64-bit memory addresses. A 64-bit register can also store 64-bit
instructions, which cannot be loaded into a 32-bit register. Therefore, most programs written
for 32-bit processors can run on 64-bit computers, while 64-bit programs are not backwards
compatible with 32-bit machines. Registers are the most important components of CPU. A
brief description of most important CPU Registers and their functions are given below:
Diagram showing registers retrieved from: https://www.geeksforgeeks.org/different-classes-

of-cpu-registers/
AC or “Accumulator Register“, register holds the integer values which are needed by the
ALU (Arithmetically Logical Unit) while executing of any specific instruction. Main
function of Accumulator Register is to store the output which is generated by your system.
When CPU (Center Processing Unit) will execute some instruction then it will produce the
result, now AC register is needed to store those produced data.
Memory Address Register (MAR): This register holds the address of memory where CPU
wants to read or write data. It holds the address of the location to be accessed from memory.
MAR and MDR (Memory Data Register) together facilitate the communication of the CPU
and the main memory.
Memory Data Registers (MDR): It contains data to be written into or to be read out from the
addressed location.
PC stands for “Program Counter” register, and it is also known as Instruction Pointer (IP) in
the Microprocessors, Program Counter register’s function is to hold all records in sequence
of entire execution of programs according to geeksforgeeks.
MDR stands for “Memory Data Register“, and this register is needed after completing the
execution in PC register. CPU fetches some mandatory instructions and data from main
memory side then its temporary copy is saved into this data register before decoding this
data. So, MDR register works as a middle buffer
Index register helps to update operand while running of the programs in the computer’s CPU.
MB register stands for “Memory Buffer Register“, and this register contains the information
of data or instruction which are read or written in the main memory. So, Memory Buffer
Register’ function is to hold all data and instruction that are fetching or going to the primary
memory side.
Data Register Mostly, these types of register are embedded into microcomputers for

temporary storing data being transmitted or from other peripheral devices.
AR stands for “Address Register“, and its main function is to hold the memory location of
instruction which is being executed. AR register contains the six registers with named (CS,
DS, ES and SS, FG, GS).
IR stands for “Instruction Register“, and this register is used to store those data which are
needed in currently execution period.
IPR stands for “Instruction Pointer Register“, and main function of this register is to hold
memory location that is executed in the next level. So, IP register stores the sequence of all
instructions that are to be performed.
SCR, “Stack Control Register“, and it is preset memory location in which data is saved and
retrieved in the specific order LIFO (Last-In-First-Out). Main function of SCR Register is to
handle the stack in the Computer System. To manage stack functionality, to use two special
registers (SP and BP).
FR register stands for “Flag Register“, and this register helps to indicate the specific
condition. Flag register contains the one or two bytes, and further every byte is splitted into 8
bits. And every bit delivers the flag means condition.
GPR stands for “General Purpose Registers“, and these are unified types of registers. These
registers are capable to store the memory addresses, data values as well as floating-point
values. Mostly, GPR registers are used into modern CPU and GPUs due to their best
flexibility.
SPR stands for “Special Purpose Registers“, and they are used to hold the program state. SPR
registers are enabled with PC (Program Counter) and SR (Status Register).
REFFERENCES
Tech terms. (2014). Registers. Retrieved from:

https://techterms.com/definition/register#:~:text=Most%20modern%20CPU%20architectures
%20include, memory%20address%20register%20(MAR).
Geeksforgeeks. (2020). Different Classes of CPU Registers. Retrieved from:

https://www.geeksforgeeks.org/different-classes-of-cpu-registers/

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NAMES : MWABA ANTHONY

Diagram showing registers retrieved from: https://www.geeksforgeeks.org/different-classes-

Data Register Mostly, these types of register are embedded into microcomputers for

Tech terms. (2014). Registers. Retrieved from:

Geeksforgeeks. (2020). Different Classes of CPU Registers. Retrieved from:

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