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W.B.C.S. Examination Notes On – Number System – Computer Science Notes.
WBCS পরীক্ষার নোট – নম্বর সিস্টেম – সংখ্যা তত্ত্ব – কম্পিউটার বিজ্ঞানের নোট।
The technique to represent and work with numbers is called number system. Decimal number system is the most common number system. Other popular number systems include binary number system, octal number system, hexadecimal number system, etc.When we type some letters or words, the computer translates them in numbers as computers can understand only numbers. A computer can understand the positional number system where there are only a few symbols called digits and these symbols represent different values depending on the position they occupy in the number.Continue Reading W.B.C.S. Examination Notes On – Number System – Computer Science Notes.
The value of each digit in a number can be determined using −
- The digit
- The position of the digit in the number
- The base of the number system (where the base is defined as the total number of digits available in the number system)
Decimal Number System
The number system that we use in our day-to-day life is the decimal number system. Decimal number system has base 10 as it uses 10 digits from 0 to 9. In decimal number system, the successive positions to the left of the decimal point represent units, tens, hundreds, thousands, and so on.
Each position represents a specific power of the base (10). For example, the decimal number 1234 consists of the digit 4 in the units position, 3 in the tens position, 2 in the hundreds position, and 1 in the thousands position. Its value can be written as
(1 x 1000)+ (2 x 100)+ (3 x 10)+ (4 x l) (1 x 103)+ (2 x 102)+ (3 x 101)+ (4 x l00) 1000 + 200 + 30 + 4 1234
As a computer programmer or an IT professional, you should understand the following number systems which are frequently used in computers.
| S.No. | Number System and Description |
|---|---|
| 1 | Binary Number System
Base 2. Digits used : 0, 1 |
| 2 | Octal Number System
Base 8. Digits used : 0 to 7 |
| 3 | Hexa Decimal Number System
Base 16. Digits used: 0 to 9, Letters used : A- F |
Binary Number System
Characteristics of the binary number system are as follows −
- Uses two digits, 0 and 1
- Also called as base 2 number system
- Each position in a binary number represents a 0 power of the base (2). Example 20
- Last position in a binary number represents a x power of the base (2). Example 2x where x represents the last position – 1.
Binary Number: 101012
Calculating Decimal Equivalent −
| Step | Binary Number | Decimal Number |
|---|---|---|
| Step 1 | 101012 | ((1 x 24) + (0 x 23) + (1 x 22) + (0 x 21) + (1 x 20))10 |
| Step 2 | 101012 | (16 + 0 + 4 + 0 + 1)10 |
| Step 3 | 101012 | 2110 |
Note − 101012 is normally written as 10101.
Octal Number System
Characteristics of the octal number system are as follows −
- Uses eight digits, 0,1,2,3,4,5,6,7
- Also called as base 8 number system
- Each position in an octal number represents a 0 power of the base (8). Example 80
- Last position in an octal number represents a x power of the base (8). Example 8x where x represents the last position – 1
Octal Number: 125708
Calculating Decimal Equivalent −
| Step | Octal Number | Decimal Number |
|---|---|---|
| Step 1 | 125708 | ((1 x 84) + (2 x 83) + (5 x 82) + (7 x 81) + (0 x 80))10 |
| Step 2 | 125708 | (4096 + 1024 + 320 + 56 + 0)10 |
| Step 3 | 125708 | 549610 |
Note − 125708 is normally written as 12570.
Hexadecimal Number System
Characteristics of hexadecimal number system are as follows −
- Uses 10 digits and 6 letters, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
- Letters represent the numbers starting from 10. A = 10. B = 11, C = 12, D = 13, E = 14, F = 15
- Also called as base 16 number system
- Each position in a hexadecimal number represents a 0 power of the base (16). Example, 160
- Last position in a hexadecimal number represents a x power of the base (16). Example 16x where x represents the last position – 1
Hexadecimal Number: 19FDE16
Calculating Decimal Equivalent −
| Step | Binary Number | Decimal Number |
|---|---|---|
| Step 1 | 19FDE16 | ((1 x 164) + (9 x 163) + (F x 162) + (D x 161) + (E x 160))10 |
| Step 2 | 19FDE16 | ((1 x 164) + (9 x 163) + (15 x 162) + (13 x 161) + (14 x 160))10 |
| Step 3 | 19FDE16 | (65536+ 36864 + 3840 + 208 + 14)10 |
| Step 4 | 19FDE16 | 10646210 |
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