1.1 Computer systems
A computer is an electronic device. A major component contained in computer are memory, storage and CPU. Computer has following specific characteristics which makes computer an essential device in recent days.
a. It is diligent. It must it can work a long time without fatigue.
b. It is reliable as long as correct input and instruction are written
c. It supports on automation as instructed.
d. It is versatile as it helps in simple word processing to machine control tasks.
1.2 Computer Hardware and Software
Definition:
Hardware: It is a physical device or component used in computer. Some examples of hardware within computer are CPU, memory, storage devices. Similarly, peripheral devices which are connected to computer are USB, monitor, printer.
Software: The program which are written to instruct computer to do task are called software. Software program generates control signals within CPU which control the operation of computer according to the program. Software level in computer are various such as operating system, application program, device drivers.
Operating system is a software where we have huge program to act as an interface between hardware and user. Similarly, application program are custom program written on user need for example word, excel etc. Device drivers has specific work to support use of device when connected to computer.
1.3 CPU: ALU, Registers, CU
CPU contains Arithmetic Logic Unit, Control Unit as two basic blocks. There are some registers available in CPU. There the term “CPU” is referring to microprocessor or core. There is system bus:
Address bus: Communication between CPU and other components is one way
Data bus: It is bi-directional bus.
Control bus: It is also bi-directional bus.
First, let us discuss on ALU. It has two components arithmetic unit and logical unit. Arithmetic unit contains adder, subtractor circuits. We study those circuits in digital logic. Logic unit circuits are also present such as to check equality between two values, find greater or less, rotating the data such as right shift or left shift.
Registers: Depending on the version of CPU, there are registers which may vary in numbers and works. Taking example of 8085 we can see register such as PC (to hold address of next instruction), Accumulator, user visible registers (B, C, D, E, H, L), stack pointer, flag register. In register, we can perform calculation or use it to store data/instruction temporarily.
Control Unit: It is the brain of CPU. It generates control signals to manage all other components. Control unit can be hardwired or microprogrammed control unit.
Hardwired control unit are designed in simple way. It takes instruction from Instruction register can use decoder to generate control signal. On the other hand, microprogrammed control unit use control memory which has atomic level of sub-operations for that instruction.
1.5 Input and Output devices
In computing, we use input and output devices. Without the use of those devices, we can’t communicate with outer world. Thus, it is essential to know how and what types of signals are transferred between them. Input devices are mouse, keyboard. Using those devices, we provide data to the computer. On the other expect, we use output devices as monitor where we can see the result produced by computer.
1.6 Operating system and application Program: It is discussed already in OS section.
1.7 Computer virus and remedies: Virus is a program which has intention to do harm in computer system. A complete program or independent program is called worm. On the other hand, a section of program in useful program can also harm computing system which is can be called as Trojan horse or virus.
While learning virus we should distinguish between independent or dependent program of malicious code. There can be virus program in data program, network program and system program which is intended to effect in all those three different areas.
We can remedy from it using anti-virus, firewall in networks.
1.8 Word processor, Spreadsheet and Powerpoint:
These applications are application program. There is a term called “off-the-shelf software”.
Computer system configuration: …..
1.9 Fonts: One is mapping ASCII codes to other. The ASCII code remains always same. Just mapping show in other fonts. For example is Preeti. Unlike, Unicode is unique for each character. Unicode is character-based encoding. No mapping is required in Unicode. Unique fonts helps us in compatibility and interoperability.