“In this life, all we have is memory! ” This exclamatory sentence is used by many film makers in their dialog.  So does it actually mean something to them?  Yes it definitely means everything to them and us.  That’s why they show them in their cinema (movie, film whatever you say).

 Memories mean everything that is stored in our brain after we experience it and then use it as a lesson for life  or entertainment purpose. Humans as well as all living beings do that.  But our topic is  “WHAT ARE REGISTERS? WHY DO COMPUTERS NEED THEM?”

So here we begin.

The discrete elements of information in a digital computer must have a physical existence in some information storage medium.  Furthermore, when discrete elements  of information are represented in binary form, the information storage medium must contain binary storage elements for storing individual bits.

  A binary cell is a device that possesses two stable states and is capable of storing one bit of information.  The input to the cell receives excitation signals that set it to one of the two states.   The information stored in a cell is 1 when it is in 1 stable state and a 0 when in other stable state.  Examples of binary cells are electronic flip-flop circuits, ferrite cores used in memory and position punched with a hole or not punched in a card.

A register is a group o binary cells.  Since a cell stores one bit of information, it follows that a register with n cells can store any discrete quantity of information that contains n bits. 

The state of a register is an n-tuple number of 1’s and 0’s with each bit designating the state of one cell in the register.  The content of a register is a function of the interpretation given to the information stored in it. 

A register with n cells can be one of 2n possible states.  Now if one assumes that the content of the register represents a binary integer,  then obviously the register can store any binary number 0 to 2n-1 .

Let us take an example 1100001111001001 this number is binary equivalent of 50121 in decimal number if the rule is about taking binary coded decimal form.  If the designer is taking 8bit registers.  Now if the cell is taking 7 bits it could denote something else.

In excess-3 code the above decimal number is 9096.  In the EBCDIC or it is termed as EXTENDED BINARY CODE DECIMAL INTERCHANGE CODE the above number is C (left eight bits) and I (right eight bits).

From this example, it its clear that a register can store one or more discrete elements of information and that the same bit configuration may be interpreted differently for different types of elements of information. 

It is important that the user store meaningful information in registers and that the computer be programmed to process this information according to the type of information  stored.


A digital computer is characterized by its registers.  The memory unit is merely a collection of thousands of registers for storing digital information.  The processor unit is composed of various registers that store operands upon which operations are performed.  The control unit uses registers to keep track o various computer sequences, and every input or output device must have at least one register to store information transferred to or from the device.


An inter-register transfer operation, a basic operation in digital systems, consist of  transfer of the information stored in one register into another.  Then this information is based on alphanumeric code which is decided by the hardware designer.  Here in alphanumeric code,  the letter which is typed by the user is converted into 8 bit code which is in the form of 1 and 0 side by side.  

The character which is typed by the user goes to  input register, in the form of 10010100(this is an example it may or may not be the same ) as the rule decided by the hardware developers.  Then on another second, the typed and converted  code is put in the processor registers where the processing takes place.  Here processor consist of registers which is internal to it.  The eight bit code is again transferred from internal register of processor to output registers of the output device.  


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