Overview of Central Processing Unit (CPU) in Computers

 All things in all posts will help you visualize about the way that computers work generally. Note that it is not the real structure of modern computers, but the way that modern computers work is nearly the same as in my posts. I am sure that if you understand about the way that computers work in my posts, you will easy to learn about all fields of computer afterward. Thank you !!!

In a previous post, you learned that RAM (random access memory) is used for storing and retrieving data in computers. And now, you can have some major questions: data is retrieved for what? Data that is stored comes from where? 

If data is stored without any previous processing, that data is meaningless because we need a computer for processing data. Processing in computers must be performed on data before storing that data in RAM. Also, data that is retrieved from RAM must be processed before being stored in RAM again.

So, computers need more things than RAM. In this post, we will briefly mention structures that are needed for processing data in computers. Let’s look at the diagram about simple computer below to understand about what I say:

At the rightmost of the diagram, you can see a RAM 256 that we learned in a previous post. You can see MAR (memory address register) that has “a” address (8-bit address) on the bus for address of memory location and “s” bit for deciding whether to set the address to MAR. You can see the memory part with the “i/o” part for data (8-bit data) on the bus, “s” bit for deciding whether to set data to memory location and “e” bit for deciding whether to transport data  that was stored on the bus.

In the diagram, the bus is the double-line (representing for 8 bits) that runs through “a” and “i/o” parts of RAM. So, the bus will connect to almost all parts of this simple computer diagram, except the control unit. The 8-bit data of “a” and “i/o” parts will always lie on the bus.

If you hide the RAM part from the diagram, you will have a central processing unit (CPU). Now, we will briefly mention every part of the CPU.

You can also see four registers: R0, R1, R2 and R3 that we also learned from a previous post. These registers have “i/o” connected to the bus for 8-bit data and have “s” bit and “e” bit connected to the control unit. “s” bit for deciding whether to set 8-bit data on the bus to register and “e” bit for deciding whether to transport 8-bit data in the registers to the bus.

The other two registers are the TMP (short for “temporary”) register and ACC (short for “accumulator”) register. The TMP register connects to the bus to receive data on the bus then outputs the data it contains to the “y” part (bus1 part that controls data from the TMP register goes into “x” part), a part of the CPU. This “y” part we will discover later, you should not worry. It also has an “s” bit that decides whether to set 8-bit data on the bus to the register.

The ACC register is the register that stores temporary data of the “x” part by connecting to the “x” part (ALU (arithmetic logical unit) that performs calculations on input data) and then connects to the bus. This register also has an “s” bit for deciding whether to store data from the “x” part and an “e” bit for deciding whether to transport data to the bus.

As you can see on the diagram, the control unit will connect to all “s” and “e” bits of all parts. This component must perform these connections because it must control all processes that occur in the computers. All parts of the computer cooperate smoothly by this control unit. We will learn more details about this control unit later.

In this post, you can understand in part about the central processing unit and control unit of computers. In next posts, we will learn more details about them and you will really understand all about it. Remember to read posts carefully. Thanks for reading and see you later!!!