Hello friends, welcome to Gate Smashers In today's video we are going to discuss different types of registers. Before starting the video, I want to tell you one thing That computer organization has always been a tricky subject for students. Because we discuss hardware and software both in this And students try to cram these concepts And because of that they are lacking in this whole subject But in all the videos I am bringing In these we'll discuss the concepts one by one in sequential order With which you will get total clarity That how actually the hardware and software works.
In the last video we discussed How we connect registers with the common bus And how we implement the common bus with the help of multiplexers Do check that video once Because you will get an idea from it That what we are talking about, about registers or different types of registers Before that you should know how we connect them How the circuit actually looks like Here we are talking about different types of registers In which we first of all talk about address register Data register, accumulator, program counter Instruction register, temporary register, input and output register Now their size, how big is the size of this register Generally the registers in our system are 16 bit Or they can be 8 bit or 32 bit But generally we use 16 bit registers Now these registers are basically sequence of bits or flip flops But how their size matters how do we measure their size that depends on this concept So first of all if you talk about memory we are talking about the memory which is RAM That is 4096*16 We have taken a very small size so that you will get to know about this concept So if we talk about memory 4096 So what is 4096 It is number of words Number of words if you are talking about a particular memory If we talk about this memory here Then how many total number of words we will have. Total number of words, now how many bits we can store in that word Means the size of the word Now I will tell you what this word is In operating system we generally talk about block But in computer organization we use this word a lot that is a "word". Now what is word actually It is a memory representational unit Means to represent memory We use word, although we use byte You must have heard about byte That memory is byte addressable But byte is actually a fixed number One byte is equal to 8 bits But today we are using operating system 32 bits, 64 bits So the size of the word is not limited to 1 byte it can be 2 bytes or 4 bytes Means multiple bytes can also be a word if we talk about memory in real life scenario Then it is word addressable So what is word here That how many words we can store in memory That is called the number of words, that is 4096 And how many bits can come in every word Means total size of that word is 16 And 16 means, bits Which you can call 2 bytes Means in our example One word is 2 bytes You can also call it like this Now if we talk about 4096 So 4096 means number of words we have 2 raised to power 12 You can write it as 2 raised to power 12 Because how we will give it numbering like this 0 0 0 0 0 Means 12 number of 0 Then 0 0 0 0 0 0 1 By doing like this at the end 1 1 1 1 1 1 Means continuously 12 "1" And in this way we will provide an address to all the words And we have to keep in that word 16 bits So 16 bits means 2 raised to power 4 You can mention it in this way also Now we will talk about address register What is the use of address register With address register We actually pick up data in memory the words in memory Now let's say I have to pick up data from a particular address That address we have to give to memory That brother pick up the word from this particular location From this particular value pick up the instruction from there So how will it happen For that we have to mention address here And that address will be in address register And with address register we will give that address to memory Memory will decode it And after decoding it will go to that particular location and fetch the data This is actually the work of address register So if we ask you what will be the size of address register According to this example what will be the size of address How many number of words we have 12 2 raised to power 12 Means from 0 to 11 So what will be the total number of size Total size of address register will be 12 bits Simple how many values are we representing address 2 raised to power 12 means 12 values are represented So address register will be of how many bits?
12 bits. Here from 0 0 0 0 to 1 1 1 continuously Any value can exist between 12 and 1 Then data register, from the name we are getting to know that data register means Where we store data Means where we bring data Now what are we putting in data register And what is the size of data How many bits can come here How many bits will be in a word. In a whole location we told the size of a word is 16 So these can be 16 bits So what is the total size of the address 0 to 15 means Total size of data register will be 16 You can ask here in this way And you should know this Because this is a very basic point We will use them later Will try to design the computer And how all these registers are connected to each other With ALU and how they are connected to each other We will see that in the next video So that you can know How we fetch the instructions How ALU executes How we keep the data temporarily on the way You will know all these points there But these points will tell you What are the registers How we measure their size Accumulator What is the use of the accumulator here We use the accumulator To store intermediate data Means if data comes from ALU we keep it In the accumulator Means in the intermediate Like we are converting the input to the output So if I have to store any particular data for a while Then we can store that data in the accumulator We picked up the data from memory After fetching the data from memory We have to give it to ALU So what can we do before that We can keep it in the accumulator for a while So what are we keeping in the accumulator Data, So what is the size of the data According to this example, 16 So what is the accumulator From 0 to 15 bits Means total number of bits is 16.
Program counter Program counter is basically we use to store the address of next instruction Means let's say that our instruction is I1 And I1 instruction is at 1000 address At 1000 number address So what is program instruction With our program counter we fetched this instruction As soon as we fetched this instruction So what is this whole area It is empty So where is the next instruction Next instruction is at 1001 Which instruction is that I2 So here the program counter that I have Program counter always points out that location Where the instruction is. Not where we picked up the instruction from This is always the next instruction Where the instruction is It will always store that particular address If we talk about this scenario currently we had already taken out the instruction from 1000 So where is the next instruction In 1001 Means what will be the value of program counter 1001 Means this point is basically telling Where our instruction is now we picked up from here. As soon as we picked up the instruction from here So where is the next instruction Let's say at 1002 So all these 7 will change to 1002 So wherever your next instruction is That address is in the program counter So again what am I saying here Address What are you keeping here Address the next instruction location or address of that place And address we have already told That how many bits are used to represent the address 12 So what is the program counter From 0 to 11 bit Or which you can simply say 12 bits Program counter.
Then instruction register this is main Because what we have to do actually We have to execute the instructions What ALU has to do, stored the program, execute that program So what do we have in memory we discussed in Von Neumann's architecture Stored memory architecture Where we keep instruction & data in same memory So what happens is that our memory in that memory Instruction is stored Instruction means let's say the format of instruction you see first In the format of instruction we have an opcode And the second is operand What are the LSB bits showing Operand means data Opcode is telling What operation you have to perform Means you have to do addition, subtraction Multiplication different types of Opcode operations will be here and where is the data That will be on operand So let's say if I write here I write add, and here I wrote 450 So what will happen What does it mean what instruction we took from there what should we do there One is addition and 450 is telling Where operand is stored Means your data is stored in memory But at which location 450 location So you go to 450 location And fetch the data from there the entire format of instruction Both these things are important That is opcode and operand Operand from where you have to pick up data That particular address And what is opcode What operation you have to perform But I have written one more thing, i The last MSB is most significant bit We keep one bit here Either 0 or 1 0 represents direct address And 1 represents indirect Addressing We will discuss about this in detail in next video But a little idea Like we discussed this example according to that Let's say I wrote add And here 450 Now here if I have this bit Which is msb If its value is 0 Means Direct address Means you go to 450 location Whatever data is there pick up that data And give it to accumulator So what is this thing telling me? It is telling address where data is there And it is telling Direct, means as soon as you go there You will get your data But if its value is 1. Means what is this?
Indirect Addressing Means you have to go to 450 first When you go to 450 On that location It may be written 1002 Means what is this? Address, now you have to go to 1002 What will you get by going there? Address These are different types of addressing modes Which we will see in detail next Now what you have to do What we are doing in instruction register We are storing the whole instruction here And instruction in our case Again 0 to 15 Means total 16 bits What is operand?
Now I have told you address that go to 450 location Go to this particular location So you know the location is 12 bit Because number of words we have According to our example 4096 So 12 is representing operand value here And the other 3 Because this bit is representing Direct and indirect So the remaining 3 bits here That is what? Opcode And what is that opcode? Addition, subtraction Multiplication, division What you have to do?
Which operation You have to perform here? So this basically is the format of instruction register And this instruction will come in instruction register what will be the size of instruction register? 0 to 15 That is 16 bits So in this way The value of registers The size we measure Next comes temporary register Temporary register means The one we use to store temporary data Again here data is stored So means 0 to 15 means 16 bits size Then we have input register Input register is To pick up data from input devices Means you typed something from keyboard So we pick up data from there And put it in input register and give that data to ALU From input register Or in accumulator so input register It has nothing to do with this Where does it take input?
It takes from input devices So in our case you take it Simply 8 bits for simplicity You can increase it That is it has nothing to do with this the data taken from input devices And such output register Obviously what we have to represent is output From where will it pick up data? It will pick up output register from ALU Now who has to be given that output? We have to give that output to output devices Like printer, scanner, monitor So to give that we use output register So these are basic registers Which we use but How is their connectivity?
How do we use this in sequence? And how is the instruction fetched? Decoded?
How do we convert it in output? We will see this in next video Here you have just given a basic idea What are different types of registers? And how do we measure their sizes?
Thank you.
