The eighth bit was originally used to check parity - a way to look for errors. IBM and Mac both created extended character sets for their personal computers, using the eighth bit to double the number of characters. As competitors, they didn't use the same characters in the same positions in their sets. Thus 8-bit character sets and incompatibility were born.
Today's standards have reduced such problems. On the Internet, many cables had wires that were designed to transmit 7-bit codes. In order to send more complex data, encoding schemes were developed to translate the more complex data e. Other reasons for the use of binary are that digital devices are more reliable, small and use less energy as compared to analog devices. Bits, bytes, nibble and word The terms bits, bytes, nibble and word are used widely in reference to computer memory and data size.
Bits: can be defined as either a binary, which can be 0, or 1. It is the basic unit of data or information in digital computers. Byte: a group of bits 8 bits used to represent a character. A byte is considered as the basic unit of measuring memory size in computer.
A nibble : is half a byte, which is usually a grouping of 4 bytes. Word: two or more bits make a word. The term word length is used as the measure of the number of bits in each word. For example, a word can have a length of 16 bits, 32 bits, 64 bits etc.
Computers not only process numbers, letters and special symbols but also complex types of data such as sound and pictures. However, these complex types of data take a lot of memory and processor time when coded in binary form.
This limitation necessitates the need to develop better ways of handling long streams of binary digits. Higher number systems are used in computing to reduce these streams of binary digits into manageable form. This helps to improve the processing speed and optimize memory usage. Number systems and their representation A number system is a set of symbols used to represent values derived from a common base or radix.
As far as computers are concerned, number systems can be classified into two major categories: decimal number system binary number system octal number system hexadecimal number system Decimal number system The term decimal is derived from a Latin prefix deci, which means ten. Decimal number system has ten digits ranging from Because this system has ten digits; it is also called a base ten number system or denary number system.
A decimal number should always be written with a subscript 10 e. X 10 But since this is the most widely used number system in the world, the subscript is usually understood and ignored in written work. However ,when many number systems are considered together, the subscript must always be put so as to differentiate the number systems.
The magnitude of a number can be considered using these parameters. Absolute value Place value or positional value Base value The absolute value is the magnitude of a digit in a number.
The place value of a digit in a number refers to the position of the digit in that number i. The total value of a number is the sum of the place value of each digit making the number. The base value of a number also k known as the radix , depends on the type of the number systems that is being used.
The value of any number depends on the radix. It uses two digits namely, 1 and 0 to represent numbers. Octal number system Consists of eight digits ranging from A hexadecimal number can be denoted using 16 as a subscript or capital letter H to the right of the number. For example, 94B can be written as 94B16 or 94BH. Further conversion of numbers from one number system to another To convert numbers from one system to another. Converting between binary and decimal numbers.
Converting octal numbers to decimal and binary form. Converting hexadecimal numbers to decimal and binary form. Write each digit under its place value. It is useful, when dealing with groups of bits, to determine which bit of the group has the least value, and which bit has the most or greatest value.
The Most significant bit is always shown on the extreme left, and is the bit with the greatest value. They can also be used to store numeric values,. The valid combinations of bits and their respective values are.
The unused nibble may be either all 0's or all 1's. This occurs in data transmission where numbers are being transmitted over a communications link. Packed BCD reduces the amount of time spent transmitting the numbers, as each data byte transmitted results in the sending of two BCD digits.
The computer handles each boolean variable as a single bit. If the bit is TRUE, then is has a value of 1. Consider the case in a program where we need to keep track of the number of minutes a phone line is busy for within the limited range of 0 to This does not require the use of a full integer, so some programming languages allow you to specify the number of bits used to allocate to variables with limited ranges.
The advantage of this approach, is that the storage space of status variables can be combined together into a single 16 or 32 bits, resulting in a saving of space. Consider where a computer allocates 16 bits of storage per status variable. If we had three status variables, the space consumed would be 48 bits. BUT, if all the status variables could be combined and fitted into a single 16 bits of storage, we could save 32 bits of memory.
We can then store this code in the computer using binary ones and zeros. ASCII code allows computers to understand how to represent text. In ASCII, each character letter, number, symbol or control character is represented by a binary value. Control characters are used to perform actions rather than to display a printable character on screen.
Easily understood examples include 'Escape', 'Backspace' and 'Delete'. Printable characters are used to show a character on screen. Letters, symbols, numbers and punctuation marks are all examples of printable characters. National 5 Subjects National 5 Subjects up.
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