How Do Computers Work?

Many people are not aware that there are more than ten different types of computers, some of which do not even have display screens often associated with these devices. In spite of the differences, however, all computers work in a generally similar way.

A computer is primarily divided into 2 major parts; hardware and software. The hardware part is composed of different components that all work together to enable the software installed to run.

Power Supply Unit (PSU)

All the great technology that goes into making a computer would be useless without the PSU. The unit takes the alternating current (AC) from a power socket, converts it into direct current (DC) and supplies different components with necessary voltage. The voltages are typically 12, 5 and 3.3 volts respectively. Fans and motors used in disk drives use 12 volts while digital circuits use either 5 or 3.3 volts.

Current computers use push buttons that are operated by a standby power (VSB) of 5 volts even when the machine is switched off. It is therefore important to plug the computer from the power supply if it will not be used for some time.

Part of the power supply unit is usually visible, particularly the openings for the cooling fan and where the power cord plugs into the system.

The PSUs are usually rated in watts. A computer with a higher rated PSU does not necessarily consume more power, as the consumption is determined by the number of drives or slots used.

Motherboard

This is the part that connects all other physical components of a computer. It enables all the components to receive necessary power and communicate. All the components either form part of the motherboard by plugging into sockets or connect to it via various ports. Form factor refers to the way the motherboard is laid out.

Central Processing Unit (CPU)

This is the microprocessor that acts as the 'brain' of the computer. Earlier CPUs had similar sets of pins, known as Pin Grid Array (PGA), which meant they could be used in any motherboard. However, different manufacturers have come up with their own PGAs.

The CPU is a full computation engine built on a single chip. Intel 4004 was the first microprocessor, which was initially used in 1971. Although the microprocessor could only subtract and add, it marked a major breakthrough. The microprocessor collects and executes machine instructions and then, depending on the instructions:

  • Moves data between different memory locations.
  • Makes decisions that help it jump to a different set of instructions.
  • Performs a variety of mathematical operations with the help of its Arithmetic/Logic Unit (ALU).

The microprocessor deals with large sets of instructions that it implements as bit patterns, which are defined by short words that humans can interpret easily. These words form what is known as assembly language. An assembler translates them to bit patterns for the microprocessor.

The CPU operates in clock cycles, measured in MHz, which is the maximum rate at which a chip can function without error. CPU speed is affected by the build-up of heat and transmission delays in the wires connecting components.

Memory

This is made up of the various components that determine the amount of storage available in a computer. This broad definition includes even the hard disk. However, the term is often used to refer to special chips that speed up the performance of a computer. If the CPU had to retrieve all needed data directly from the hard disk at all times, a computer would be frustratingly slow. These chips provide temporary data storage for quick access.

A memory chip is composed of millions of capacitors and transistors in an integrated circuit just as a microprocessor. The capacitors contain relevant data while the transistors are the switches that put or empty the data. For example, transistors fill capacitors with electrons to store 1 and empty them to store 0. Computers use binary system, which is made of a series of 0s and 1s.

There are different types of memory, with the most common being Random Access Memory (RAM) and Read-only Memory (ROM). If a computer is slow, adding more RAM can lead to better performance than replacing the CPU. Flash memory is a type of ROM that plays an important role, as will be explained later.

Buses

Just as buses carry people to and from different places, computer buses transfer data within a computer as well as between it and other devices. The difference is that the computer buses are also the highways, which means they do not move. They include things like SCSI, PCI, serial ports, parallel ports and USB ports.

One of the major advantages of buses is that they make it easy to interchange components. There are 2 primary types of buses in a typical computer.

The system bus connects the CPU and system memory. The other type of bus connects other components like sound cards and hard disks, with the most common being the PCI (Peripheral Component Interconnect). They connect to the system bus via a bridge, which integrates data from different buses before sending them to the system bus.

Software

Basically, software refers to the various programs a computer requires to perform necessary actions.

Operating System

The operating system has 2 primary functions:

  • Managing all the software and hardware resources in a computer. This is important because some functions and programs compete for memory and CPU resources. It acts as a parent who ensures everyone gets a good share.
  • Providing applications with a consistent and stable way of dealing with hardware without knowing details of respective pieces of hardware. This allows things to keep running smoothly even after updates and upgrades.

The operating system also provides the basic computer user interface.

There are different types of operating systems, including real-time operating system (RTOS), single-user/single task, single-user/multi task and multi-tasking systems.

BIOS

This is the acronym for basic input/output system, which is where flash memory is most commonly used. All computers require BIOS to ensure the CPU, hard drives, various chips and ports function together.

The main function of BIOS is loading the operating system by providing relevant instructions to the microprocessor. The CPU cannot take its initial instructions from the operating system, which is stored in a hard drive, when the computer is turned on.

Once the computer has been turned on, BIOS will first check information stored on a small RAM found on a CMOS (complementary metal oxide semiconductor) chip. It then modifies its default programming as per current needs based on the information retrieved.

BIOS acts as a bridge between the operating system and important hardware components. This special software is usually stored on flash memory.

All the things discussed take place within the computer itself. Other important components are input devices like keyboards and mice as well as display devices like the monitor.


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