A computer is a programmable device that responds to a specific instruction sets which are stored in its own memory. It is able to execute different functions such as manipulating the data, producing the specific results and storing the results in a specific location.
There are two main subcategories of a computer: Computer Architectures and Operating Systems.
Computer Architecture refers to the conceptual design and operational structure of a computer system. It focuses on the organization, implementation and performance of the basic building blocks of the computer system, focusing mainly on the central processing unit (CPU).
An operating system refers to the software that manages the computer hardware resources in order to organize and control hardware and software of the operating device.
Computer Architectures and Operating Systems would interact through an interface that exchanges run-time information and application progress.
Program Control Unit
CC)
Arithmetic Logic Unit
CC)
Central Processing Unit (CPU).
(William Stallings, Page 19)
I/O Devices
Main Memory
User
Operating Systems
Applications
Hardware
Operating Systems (OS)
Computer System
A computer system allows the user to perform four basic functions such as the input, processing, storage and the output of the different data. The Central Processing Unit (CPU) is the main unit that performs the processing of the different data.
Input / Output Devices (I/O Devices)
An Input / Output (I/O) device is a hardware that is able to accept inputted information from the user or from a peripheral device. Similarly, it also has the same capability in outputting the same information as well. Examples of the I/O devices are hard drive and CD-ROM drives.
Input / Output (I/O) devices are both connected to the computer. The main difference between them is the flow of data towards the computer.
Input devices
Output devices
Computer
Keyboard
Mouse
Headphones
Printers
Input Devices
Input devices are able to convert the information inputted by the user into a form of language that is acceptable by the computer. It serves as a communication tool between the computer and the user. Devices such as keyboards and mouse are examples of input-only devices.
Therefore, the input device is responsible for conversion of the data format that is suitable for human communication to a format that is acceptable for the computer.
Input devices
Computer
Keyboard
Mouse
Input devices
Input Devices
Output devices refer to any types of peripheral devices that are able to receive or display the output from a computer. Headphones and printers are examples of an output-only device.
Therefore, the output device is responsible for conversion of the data format that is oriented by the computer to a format that is acceptable for human communication.
Output devices
, Computer
Headphones
Printers
Output devices
Memory
Computers usually store data in a digital format. Memory refers data storage that comes in the form of chips. It is used to store programs and data on a temporary or permanent basis in a computer. Capacitors and transistors are used for temporary memory storage while disks with a magnetic coating are used for permanent memory storage. Memory serves as the is the main resource which holds both the programs and data.
Computer Memory Hierarchy
Processor Registers
Level 1 Cache
Level 2 Cache
Level 1 Cache
Random Access Memory (RAM)
Level 1 Cache
Non-Volatile Memory
Level 1 Cache
Virtual Memory
Level 1 Cache
Temporary Storage
Permanent Storage
Computer memory could be organized into a hierarchy in order to differentiate the different access of the memory. Processor registers are classified as the highest level of the hierarchy. It is able to operate at a very high speed. Cache is classified as the second level of the hierarchy. There could be multiple levels of cache being used at this level. The CPU cache is an example for faster access time and frequent use of memory. Main Memory is classified as the third level of the hierarchy. It is usually made up of random access memory (RAM). Non-Volatile memory such as flash disks made up the fourth level of the hierarchy. At this level, the devices operate at an average speed. The last level of the hierarchy is made up by the virtual memory. Devices at this level are able to store data at the cheapest rate compare to any other memory in the hierarchy. Therefore, the devices classified under different levels and types of hierarchy would have different uses.
Central Processing Unit (CPU)
The Central Processing Unit (CPU) refers to the hardware within a computer system that will carry out the different instruction sets of a computer program. Most calculations would take place in the CPU. There are two main subcategories of the CPU: Control Units (CU) and Arithmetic Logic Unit (ALU).
Control Units (CU)
The control unit (CU) would coordinate with different components of the computer system by fetching the codes of all of the instructions sets in the program. It would control its operation that sends signals to various parts in the system to perform certain functions. Computer resources are usually being managed by the control unit. Besides that, it also directs the flow of data between the CPU and the other devices.
Arithmetic Logic Units (ALU)
An arithmetic logic unit (ALU) refers to a digital circuit which is made up of several logic gates. It is able to conduct arithmetic and logical computation. Arithmetic logic unit serves as the core of the CPU. The control unit would transmit a signal to the arithmetic logic unit in order for the ALU to process the data. The processed data could be stored into the main memory.
Program Control Unit
CC)
Arithmetic Logic Unit
CC)
Central Processing Unit (CPU).
(William Stallings, Page 19)
I/O Devices
Main Memory
(IV) Model of Computer System
(e)
(b)
(c)
(d)
(c)
(d)
(a)
(a)
(f)
(f)
(William Stallings, Page 19)
Output: Headphone Printers
Input: Keyboard Mouse
External: Flash Drive Hard Disk
Internal: RAM Cache
Memory and Storage Devices
Input / Output Devices (I/O Devices).
Central Processing Unit (CPU).
Arithmetic Logic Unit
CC)
Program Control Unit
CC)
Instructions and data are being sent as inputs into the arithmetic logical unit and the control unit.
While the arithmetic logical unit is processing the input from the I/O devices, it communicates with the control unit by exchanging the instruction sets, data and signals.
Data could be stored in the internal memory or external memory, depending on the nature of work.
The stored data is being retrieved and transmitted.
While the arithmetic logical unit is processing the output from the memory and storage devices, it communicates with the control unit by exchanging the instruction sets, data and signals.
The processed data is now sent back to the output device with instruction sets, data and signals.
