Converting a Hexadecimal Number to a Decimal Number

We can use the same method that we used to convert binary numbers and octal numbers to decimal numbers to convert a hexadecimal number to a decimal number, keeping in mind that we are now dealing with base 16. From right to left, we multiply each digit of the hexadecimal number by the value of 16 raised to successive powers, starting with the zero power, then sum the results of the multiplications. Remember that if one of the digits of the hexadecimal number happens to be a letter A through F, then the corresponding value of 10 through 15 must be used in the multiplication.

Example 1: Convert the hexadecimal number 20B316 to its decimal equivalent

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Example 2: Convert the hexadecimal number 12AE516 to its decimal equivalent.

Converting a Decimal Number to a Hexadecimal Number

Example1: Convert 926310 to its hexadecimal equivalent:

Divide 16 into 9263. The quotient is 578 with a remainder of 15; so indicate the hex equivalent, "F", on the right.

Divide 16 into 578 (the quotient from the previous division). The quotient is 36 with a remainder of 2, indicated on the right.

Divide 16 into 36. The quotient is 2 with a remainder of 4, indicated on the right.

Divide 16 into 2. The quotient is 0 with a remainder of 2, as indicated. Since the quotient is 0, stop here.

Hexadecimal Addition Examples

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2) Here is another example with carries

Converting Binary-to-Octal or Octal-to-Binary

To convert from binary to octal, divide the binary number into groups of 3 digits starting on the right of the binary number. If the leftmost group has less than 3 bits, put in the necessary number of leading zeroes on the left. For each group of three bits, write the corresponding single octal digit.

To convert from octal to binary, write the corresponding group of three binary digits for each octal digit.

COMPUTER HARDWARE

After learning this chapter the students will be able to:

• Understand functional units of computer, learn about various input/output devices, secondary storage devices;
• Understand data and instruction flow using communication buses and ports;
• Describe a general-purpose computer system: Major functions of systems: input, processing, output, storage.
• Explain the functions of the major hardware components of a computer system: Central Processing Unit (CPU): control unit and ALU; main memory/immediate access storage, secondary storage, input/output devices.
• Outline the functions and uses of primary storage devices: Bistable devices, PROM, EPROM, RAM, ROM.
• Manipulate units of storage: Bit, byte, kilobyte, megabyte, gigabyte, terabyte, word, word size.
• Compare the types of secondary storage media with respect to portability, speed and capacity: Magnetic tape, floppy disk, hard disk (fixed head, moving head, external), optical disks (CD, DVD), flash drive, flash memory cards.
• Use terms associated with storage devices: Read/write head, sectors, tracks, buffers, cylinders, access time, sequential access, direct access; device interfaces such as: SCSI, IDE, SATA.
• Explain the uses of various input devices and media: Optical mark reader (OMR), character readers (OCR, MICR), mouse, joystick, bar code reader, document scanner, light-pen, touch terminals, voice response unit, pads and tablets, point of sale (POS), keyboard, digital camera, biometric systems, sensors, remote control, sound capture, pointing devices, webcam.
• State the types and functions of output devices: Visual display unit: resolution, types, sizes. Printers: impact and non-impact, types: (character, line, page, laser, inkjet, dot matrix). Characteristics: (speed, quality, storage capacity); plotters; audio output devices (for example, speakers, head-phones, earphones); microfilm. Also terms such as hard copy, soft copy, human readable and machine–readable.

Our present day life is so automatic that most of the tasks are accomplished with a click of a button. Washing has been taken over by washing machines, cooking by microwaves, conventional banking has been replaced by ACMs etc. In every sphere of life, machines dominate human efforts. Have you ever wondered what mechanism works behind these machines? In fact, in all these machines, a click of button starts a process inside the machine which sometimes can be very complex one. It does exactly what is required as it follows a predefined work flow based on which button has been pressed. Let us take the case of cash withdrawal from a bank ACM. The user is required to press only a few buttons to authenticate his card number, pin-code and the amount he wishes to withdraw. Then within seconds the money pops out of the ACM. During this process, the inside working of bank ACM is beyond imagination of the user. Broadly speaking, the ACM receives certain data from the user, processes it and gives the output (money). This is exactly what a computer does. Formally, a computer can be defined as follows: A computer is an electronic device that processes input data and produces result (output) according to a set of instructions called program.

A computer performs basically five major functions irrespective of its size and make.

· It accepts data or instructions by way of input

· It stores data

· It processes data as required by the user

· It controls operations of a computer

· It gives results in the form of output

In order to carry out the operations mentioned above the computer allocates the task among its various functional units.

Figure 2.1Block diagram of functional units of a computer

The above diagram describes the basic layout of a computer. A computer receives data and instructions through "Input Devices" which get processed in Central Processing

Unit, "CPU" and the result is shown through "Output Devices". The "Main / primary Memory" and "Secondary / Auxiliary Memory" are used to store data inside the computer. These are the basic components that each computer possess. Each of these components exists in various types and variety that differ in shape, size, usage and performance. The user makes a choice according to his specific requirement. Now we will discuss each component in detail.

Input Devices

These are used to enter data and instructions into the computer. Let us discuss some of

them.

Keyboard

This is the most common input device which uses an arrangement of buttons or keys. In a

keyboard each press of a key typically corresponds to a single written symbol. However some symbols require pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or characters, other keys or simultaneous key presses can produce actions or computer commands. In normal usage, the keyboard is used to type text and numbers while in a modern computer, the interpretation of key press is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports the key-presses to the controlling software. Keyboards are also used for computer gaming, either with regular keyboards or by using keyboards with special gaming features. Apart from alphabet keys (26 keys), there are several other keys for various purposes such as

· Number keys - The 10 number keys 0-9 are there on each keyboard. Sometimes, there are two sets of these keys.

· Direction keys - There are four direction keys: left, right, up and down which allow the curser to move in these directions. Unlike alphabet and number keys, these keys do not display anything.

· Function keys - There are generally 12 functions keys F1-F12. These keys have special tasks and the tasks may change from program to program. Just like direction keys, these too do not print anything.

· Other keys - There are several other non-printable keys for various different purposes. These include caps lock, tab, ctrl, pause, delete, backspace, spacebar and shift, enter etc. which are used for special purposes

Figure 2.2 Keyboard Layout

Whenever a key is pressed, a specific signal is transmitted to the computer. The keyboard uses a crossbar network to identify every key. When a key is pressed, an electrical contact is formed. These electric signals are transmitted to a microcontroller in a coded form to the computer describing the character which corresponds to that key. The theory of codes in itself is a vast field of study. However, in Appendices I, II, III and IV we have discussed the most common codes namely BCD, ASCII, ISCII and Unicode.

All programs and software were mostly text-based. With the subsequent GUI based operating systems, more application based software were evolved and in addition to keyboard, more sophisticated input devices were also evolved such as mouse, joystick, scanner etc. We discuss these devices below.

Mouse

Date: 2015-12-17; view: 957