1.1 Electronic Computers Then and Now

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1 1.1 Electronic Computers Then and Now The first electronic computer was built in the late 1930s by Dr.John Atanasoff and Clifford Berry at Iowa State University in USA. They designed their computer to assist graduate students in nuclear physics with their mathematical calculations. The first large-scale, general purpose electronic digital computer, called the ENIAC, was completed in 1946 at the University of Pennsylvania with funding from the US army. These early computers used vacuum tubes as their basic electronic component. Today new generations of computers were considerably smaller, faster, and less expensive than previous ones. Using today s technology, the entire circuitry of a computer processor can be packaged in a single electronic component called a computer or microprocessor chip. These chips are installed in watches, PDS s (Personal Digital Assistance), GPS systems, cameras, home appliances, automobiles, and of course computers. Modern computers are categorized according to their size and performance. Personal computers : Used by a single person Mainframes: Large, very powerful, real-time transaction processing systems, banking networks, ATMs reservations systems for airline, motels, etc.. Supercomputers: Largest capacity and fastest computers, used by research laboratories and computationally number crunching application such as weather forecasting. The elements of a computer system fall into two major categories: Hardware and Software. Hardware is the equipment used to perform the necessary computations and includes the central processing unit(cpu), memories, monitor, keyboard, mouse, printer, and spiker. Software consist of the programs that enable us to solve problems with computer by providing it with lists of instruction to perform. 1.2 Computer Hardware Hardware of a computer consist of the following components: Main memory Secondary memory, which includes storage devices such as hard disks, CDs, DVDs, and flash drives. Central processing unit. Input devices, such as keyboards, mouse, touch pads, scanners, joysticks Output devices, such as monitors, printers, and speakers.

2 Memory Consists of memory cells, which is consist of ordered sequence of storage locations. Address of a memory cell : the relative position of a memory cell in the computers s main memory. Contents of a memory cell : The information stored in a memory cell, either a program instruction or data. Bits and Bytes : Binary refers to a number system based on two numbers, 0 and 1, so a bit is either a 0 or a 1. Generally there are eight bits to a byte. Storage and Retrieval of Information in Memory: A computer can either store a value into a memory interims of binary number representations or retrieve a value from the memory Main Memory :Main memory stores programs, data and results. Most computers have two types of main memory. Random-Access-Memory(RAM) :Used for temporary storage of programs and data. Everything in RAM will be lost when the computer is switch is off. Read-Only-Memory(ROM) : Used for permanently storage of programs and data. The computer can retrieve, but cannot store, information in ROM, hence its name, read-only. Secondary Storage Devices: These devices are used to store huge amount of information. These are Hard disk, CDs,DVDs and flash memories. Hard Disk :Hard disks are attached to their disk drives and coated with a magnetic material. Each data bit is a magnetized spot on the disc, and the spots are arranged in concentric circles called tracks. The disc drive read/write head accesses data by moving across the spinning disk to the correct track and then sensing the spots as they move by. Hard discs hold from one to several hundred gigabytes(gb) of data, but clusters of hard drives that stores data from an entire network may provide as much as a terabyte(tb) of storage. Term Abbreviation Equivalent to Comparison to Power of 10 Byte B 8 Bits KiloByte KB 1,024 (bytes) >10**3 MegaByte MB 1,048,576(bytes) >10**6 GigaByte GB 1,073,751,824(bytes) >10**9 TeraByte TB 1,099,511,627,776(bytes) >10**12 1

3 Input devices (Keyboards, Mouse, Touch Pads, Scanner, Joystick) Main Memory Central Processing Unit(CPU) Output devices (monitor, Printer, Speaker,) Secondary Storage (Disk,Falsh Memory, DVD,CD) Components of a Computer Optical Drives :For storing and retrieving data on compact discs(cds) or digital versatile disks(dvds) that can be removed from the drive. One CD can hold 680 MB of data. A DVD uses smaller pits packed in a tighter spiral, allowing storage of 4.7 GB of data one one layer. Some DVDs can hold four layers of data- two on each sidefor a total capacity of 17 GB, sufficient storage for as much as nine hours of studioquality video and multi-channel audio. Flash Drive(USB)(Universal Serial Bus):Flash drives(stick memory) have no moving parts and all data transfer is by electronic signal only. Typical USB flash drives store 1 to a few GB of data, but 64 GB drives are also available. Information stored on a disk is organized into separate collections called files: One file may contain a C program. Another file may contain the data to be processed by the program(a data file) or a file may contain a picture information. A file could contain results generated by a program(an output file). The names of all files stored on a disk are listed in the disk s directory. This directory may be divided into one or more levels of subdirectories or folders. 2

4 Central Processing Unit The Central Processing Unit(CPU) has two roles. A)Coordinating Operations of Computer B)Performing Arithmetic and Logical operations on data. The CPU follows the instructions contained in a computer program to determine which operations should be carried out and in what order. The CPU stores the results in main memory. The CPU can perform such arithmetic operations as addition, subtraction, multiplication, and division. The CPU can also compare the contents of two memory cells and make decision based on the result of that comparison. A CPU s current instruction and data values are stored temporarily inside the CPU in special highspeed memory locations called registers(high speed memory location). Input/Output Devices We use Input/Output devices to communicate with the computer. They allow us to enter data for a computation and to observe the results of that computation. We use a keyboard as an input device and monitor(display screen) as an output device. A keyboard has keys fro letters, numbers, and punctuation marks plus some extra keys for performing special functions. A mouse is an input device used to select an operation. A monitor provides a temporary display of the information that appears on its screen. If you want a printed version(hard copy) of some information you must sent that information to an output device called printer. Computer Networks Computers are linked together in networks so they can be communicate with one another. In a local area network(lan), computers and other devices in a building are connected by cables or wireless network, allowing them to share information and resources such as printers, scanners, and secondary storage devices. A computer that controls access to a secondary storage devices such as a large hard disk is called a file server. A network that links many individual computers and local are networks over a large geographics area is called a wide area network(wan). The most well known WAN is the Internet, a network of university, corporate, government, and public-access networks. The Internet is designed by the US Defense Department s 1969 ARPAnet Project. The most widely used aspect of the internet is the World Wide Web(WWW), the universe of Internet-accessible resources that are navigable through the use of a graphical user interface(gui). 3

5 If you have a computer with a modem, you can connect to the information through a telephone line or television or fiber-optic cable. A modem(modulator/demodulator) converts binary computer data into audio tones that can be transmitted to another computer over a normal telephone circuit. At the computer on th receiving end, another modem converts the audio tones back to binary data. Today s modems transmit over 50,000 or 100,000 bits per second or if you have a digital subscriber line (ADSL), the associated modem can transmit 1.5 million bits per second. 1.3 Computer Software Mainly there are two main software groups in a computer. These are Operating system(os) and Application software. Operating System To make the hardware friendly to the user operating system is used. The collection of computer programs that control interaction of user and computer hardware is called Operating System. Most of the operating system are written using C language and has a lot of sub modules in it. OS manages allocation of computer resources. Usually part of the OS is stored permanently in a read-only memory (ROM) chip work as a starter of the operating system is called booting the computer. Here is a list of some of the operating System s capabilities. Communicating with the computer user. Managing allocation of memory, of processor time, and of other resources for various task. Managing Input/Output operations among the user programs and OS. Accessing data from secondary storage. Writing data to secondary storage. Command-Line Interface UNIX MS-DOS VMS Graphical User Interface Macintosh OS Windows OS/2 Warp UNIX + X Window System Widely Used Operating System Families Categorized by User Interface Type Application Software Application programs are developed to assist a computer user in accomplishing specific task. For example, a word-processing application MS Word, WordPerfect, or a spreadsheet application Lotus or Excel programs or a database management application such as Access or dbase systems are well known application programs. User can also create their own application programs by using any programming language and solve a specific problem. 4

6 Computer Languages To solve a given problem using computer, user prefer high-level programming languages. There are many high-level programming languages are available these days. Language Application Area Origin of Name FORTRAN Scientific Formula Translation COBOL Business data processing Common Business Oriented Language LISP Artificial Intelligence List Processing C System programming Predecessor language was named B Prolog Artificial Intelligence Logic Programming Ada Real-Time distributed sys. Ada Augusta Byron Collaborated.. Smalltalk GUI Objects talk to one another with message C++ Support OOP Incremental modification of C C# Support OOP,General purpose VisualBasic Support OOP,General purpose Java Supports web programming Source file is written by a programmer for the solution of a specific problem. A source file containing the text of a high-level language program. The software developer creates this file by using an editor or word processor. Using a compiler this source program is compiled. During compilation grammar rules are checked.(syntax checking) If the program is syntactically correct, compiler saves in an object file. Object file consist of machine language instructions. Using linker program object file is converted into machine language code which is an executable file and ready to run. Running this file given problem will be solved. 5