Introduction to Computers
Today, Computer play an important role in our day-to-day life. In fact, we are dependent on computers to a great extent. Computers have made our lives easier, be it railway or airline reservation, movie tickets, telephone and electricity bills, hospitals - the list of computer usage is endless.
For example, earlier we had to stand in long queues to book our tickets at the ticket counter but now we can book tickets in a few minutes through the internet.
Although computer is more informed and more intelligent than man, still it cannot work without our instructions. It cannot perform any task without us. The computer needs to be given a set of instructions to perform a particular task.
Before we proceed to the working of a computer, let us first recall the journey of computers through different generations.
Generation of Computers
Over the past few decades, computers have evolved depending on our requirements. This growth is referred to as 'Generation of Computers.' Each generation of computers is characterized by a major technological development that changed the way computers operate. This resulted in increasingly smaller, cheaper, more powerful, more efficient and reliable devices.
1. First Generation: The first computers used vacuum tubes for circuitry and magnetic drums for money and were often extremely large in size, occupying an entire room. They were also noisy and created pollution.
2. Second Generation: Components used were transistors. The transistors were far superior to vacuum tubes, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than the first-generation computers. These were also the first computers that stored instructions in their memory which moved from a magnetic drum to magnetic core technology.
3. Third Generation: In this generation of computers, components used were Integrated Circuits. The transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers.
4. Fourth Generation: In this generation, components used were micro-processors. Thousands of integrated circuits were built on to a single silicon chip.
5. Fifth Generation: The fifth generation infused intelligence into computers called Artificial Intelligence. This is today's generation of computers and devices are still being developed. There are some applications, such as voice recognition, that are being used today to give commands to these computers.
Computer Systems and Their Basic Features
Computer systems are categorized based on the size, cost and performance. The most common and most popular computer system we know today is Personal Computer (PC), also known as desktop computer. A PC is small in size and is capable of doing various things. It can be used for performing multiple tasks at a time. PCs are designed to be used by one person at a time.
Mobile computers are a kind of personal computers/ microprocessors that are small and light enough for a person to carry from one place to another. These are divided into following categories:
1. Laptop: It is a portable computer which can be carried from place to place. It has a small alphanumeric keyboard and an LCD computer screen, which can be folded and transported easily. It is designed in a notebook shape in the flip form factor to protect the screen and keyboard when closed.
2. Ultrabook: It is a very thin and light laptop.
3. Tablet: It is like a laptop or ultrabook computer but without the keyboard. We can operate a tablet via touchscreen.
4. Smartphone: A mobile phone with internet connectivity is known as smartphone. We operate it via touchscreen. Voice calling, text messages and camera are some of the important features of a smartphone.
Another type of computer system is Mini Computer, which is a small, general-usage computer. It is more expensive than a pc, has relatively high processing power and more storage capacity. A Mini Computer is designed for multiple users, i.e. more than one person can work on it at the same time.
Mainframe is another form of computer system, which is more powerful than a Mini Computer. It is very expensive as its performing capability is very high. These are typically used by large organizations as they have large scale data for processing, such as web servers.
The largest, fastest, most accurate and the most expensive of all types of computer systems in the world are Supercomputers. These are mostly used for scientific and defence applications.
Game Consoles are devices which are used to play video games. The player interacts with the game through a controller, a hand held device with buttons and joysticks. Video and sound are received through a television. For example, Xbox and Sony Playstation.
Embedded computers are not stand alone computers. These are incorporated into some other device. All the applications having digital interface use embedded systems. For example, digital camera, washing machine, microwave, cars, watches.
Types of Computer Languages
Computers do what we tell them to do with the help of a program. A computer program is written in a programming language. Nowadays, writing computer program is very easy as we write them in a language that is almost like English. Earlier, it was not as easy as these languages did not exist. Computer languages have evolved over time. We will briefly learn how new programming languages have emerged over the years.
Computer is an electronic device and can have either an ON state or an OFF state, which is like saying either it understands 1 or 0. All computers understand every instruction and data in a combination of 1s and 0s. We have learnt in Mathematics that when we represent numbers with the help of 1 and 0, it is known as binary number system. Computers understand binary language.
Features of Low-Level Languages
Initially, computer programs were written in Low-Level languages or binary language, also known as machine language. Cards were punched to store the binary or machine language commands and then these were fed into the computer. Instructions and data were represented with a combination of 1s and 0s. This method of writing programs was very tedious and complicated. If a single mistake occurred in punching the card, the card had to be discarded and a fresh card had to be re-punched.
In today's world, this language is used only by the programmers who write programs at the system level. This language enables them to write code for drivers, interfaces with hardware devices, etc.
Advantages
The main advantage of machine language is that the code takes very little time to execute. It runs very fast and very efficiently as the instructions are easily understood by the CPU. No translation of the program is required.
Limitations
Machine language has the following limitations:
1. Machine-dependent: This language is specific to a type of computer. Therefore, a program written on one machine cannot be easily transferred to another machine.
2. Difficult to program: To do programming in machine language, it is necessary for a programmer to memorize the number codes of the instructions.
3. Errors: The programmer is prone to making errors.
4. Difficult to modify: It is very difficult and time-consuming to check for errors or to modify the machine language programs.
Features of Assembly Language or Second Generation Language
As coding in Machine language was cumbersome, it became imperative to develop a language that was relatively simple to program in.
Thus, a new language of symbols, known as assembly language, emerged. It helped in overcoming the limitations of machine language by-
Using alphanumeric codes, instead of number codes. For example, ADD instead of 1110 (binary code), SUB instead of 1111 (binary code).
Allowing programmers to easily locate the storage location by using alphanumeric addresses.
Programmers were able to write programs in assembly language with relative ease as compared to machine language. Though the programmers were saved from remembering binary numbers for operations, they had to now remember symbols instead. As a computer understood only machine language, the language had to be converted into machine language for the computer to execute the program. The programs that converted the assembly programs into machine language were called assemblers.
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