Data types in C programming
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The document discusses basic data types in C programming including characters, integers, floating point numbers, and how they are represented in memory. It explains that all data is stored as sequences of bits and describes the common basic data types in C like char, int, float, and double. It also discusses how integers are represented using binary, hexadecimal, and two's complement representations and how this affects the range of positive and negative numbers that can be stored.
![CoxSimple Data Types10
ASCII
From “man ascii”:
| 0 NUL| 1 SOH| 2 STX| 3 ETX| 4 EOT| 5 ENQ| 6 ACK| 7 BEL|
| 8 BS | 9 HT | 10 NL | 11 VT | 12 NP | 13 CR | 14 SO | 15 SI |
| 16 DLE| 17 DC1| 18 DC2| 19 DC3| 20 DC4| 21 NAK| 22 SYN| 23 ETB|
| 24 CAN| 25 EM | 26 SUB| 27 ESC| 28 FS | 29 GS | 30 RS | 31 US |
| 32 SP | 33 ! | 34 " | 35 # | 36 $ | 37 % | 38 & | 39 ' |
| 40 ( | 41 ) | 42 * | 43 + | 44 , | 45 - | 46 . | 47 / |
| 48 0 | 49 1 | 50 2 | 51 3 | 52 4 | 53 5 | 54 6 | 55 7 |
| 56 8 | 57 9 | 58 : | 59 ; | 60 < | 61 = | 62 > | 63 ? |
| 64 @ | 65 A | 66 B | 67 C | 68 D | 69 E | 70 F | 71 G |
| 72 H | 73 I | 74 J | 75 K | 76 L | 77 M | 78 N | 79 O |
| 80 P | 81 Q | 82 R | 83 S | 84 T | 85 U | 86 V | 87 W |
| 88 X | 89 Y | 90 Z | 91 [ | 92 | 93 ] | 94 ^ | 95 _ |
| 96 ` | 97 a | 98 b | 99 c |100 d |101 e |102 f |103 g |
|104 h |105 i |106 j |107 k |108 l |109 m |110 n |111 o |
|112 p |113 q |114 r |115 s |116 t |117 u |118 v |119 w |
|120 x |121 y |122 z |123 { |124 | |125 } |126 ~ |127 DEL|
Special
control
characters](https://image.slidesharecdn.com/datatypesweek4-190304175253/85/Data-types-in-C-programming-10-320.jpg)
Data types in C programming
- 2. Objectives • Be able to explain to others what a data type is • Be able to use basic data types in C programs • Be able to see the inaccuracies and limitations introduced by machine representations of numbers CoxSimple Data Types2
- 3. What do you see? CoxSimple Data Types3
- 4. What do you see? CoxSimple Data Types4
- 5. Last one CoxSimple Data Types5
- 6. CoxSimple Data Types6 Everything is Just a Bunch of Bits • Bits can represent many different things • Depends on interpretation • You and your program must keep track of what kind of data is at each location in the computer’s memory • E.g., program data types
- 7. CoxSimple Data Types7 Big Picture • Processor works with finite-sized data • All data implemented as a sequence of bits • Bit = 0 or 1 • Represents the level of an electrical charge • Byte = 8 bits • Word = largest data size handled by processor • 32 bits on most older computers • 64 bits on most new computers
- 8. CoxSimple Data Types8 Data types in C •Only really four basic types: • char • int (short, long, long long, unsigned) • float • double •Size of these types on •CLEAR machines: •Sizes of these types •vary from one machine •to another! Type Size (bytes) char 1 int 4 short 2 long 8 long long 8 float 4 double 8
- 9. CoxSimple Data Types9 Characters (char) • Roman alphabet, punctuation, digits, and other symbols: • Encoded within one byte (256 possible symbols) • ASCII encoding (man ascii for details) • In C: char a_char = ’a’; char newline_char = ’n’; char tab_char = ’t’; char backslash_char = ’’;
- 10. CoxSimple Data Types10 ASCII From “man ascii”: | 0 NUL| 1 SOH| 2 STX| 3 ETX| 4 EOT| 5 ENQ| 6 ACK| 7 BEL| | 8 BS | 9 HT | 10 NL | 11 VT | 12 NP | 13 CR | 14 SO | 15 SI | | 16 DLE| 17 DC1| 18 DC2| 19 DC3| 20 DC4| 21 NAK| 22 SYN| 23 ETB| | 24 CAN| 25 EM | 26 SUB| 27 ESC| 28 FS | 29 GS | 30 RS | 31 US | | 32 SP | 33 ! | 34 " | 35 # | 36 $ | 37 % | 38 & | 39 ' | | 40 ( | 41 ) | 42 * | 43 + | 44 , | 45 - | 46 . | 47 / | | 48 0 | 49 1 | 50 2 | 51 3 | 52 4 | 53 5 | 54 6 | 55 7 | | 56 8 | 57 9 | 58 : | 59 ; | 60 < | 61 = | 62 > | 63 ? | | 64 @ | 65 A | 66 B | 67 C | 68 D | 69 E | 70 F | 71 G | | 72 H | 73 I | 74 J | 75 K | 76 L | 77 M | 78 N | 79 O | | 80 P | 81 Q | 82 R | 83 S | 84 T | 85 U | 86 V | 87 W | | 88 X | 89 Y | 90 Z | 91 [ | 92 | 93 ] | 94 ^ | 95 _ | | 96 ` | 97 a | 98 b | 99 c |100 d |101 e |102 f |103 g | |104 h |105 i |106 j |107 k |108 l |109 m |110 n |111 o | |112 p |113 q |114 r |115 s |116 t |117 u |118 v |119 w | |120 x |121 y |122 z |123 { |124 | |125 } |126 ~ |127 DEL| Special control characters
- 11. CoxSimple Data Types11 Characters are just numbers •What does this function do? Char fun(char c) { char new_c; if ((c >= ’A’) && (c <= ’Z’)) new_c = c - ’A’ + ’a’; else new_c = c; return (new_c); } return type procedure name argument type and name local variable type and name Math on characters! comparisons with characters!
- 12. CoxSimple Data Types12 FP vs. Integer Results int i = 20 / 3; float f = 20.0 / 3.0; True mathematical answer: 20 3 = 6 2/3 i = ? f = ? 6 6.666667 Integer division ignores remainder FP arithmetic rounds result
- 13. CoxSimple Data Types13 Integer Representations Base 2 Base 16 Unsigned 2’s Comp. 0000 0 0 0 0001 1 1 1 0010 2 2 2 0011 3 3 3 0100 4 4 4 0101 5 5 5 0110 6 6 6 0111 7 7 7 1000 8 8 -8 1001 9 9 -7 1010 A 10 -6 1011 B 11 -5 1100 C 12 -4 1101 D 13 -3 1110 E 14 -2 1111 F 15 -1 0000 0001 0010 0011 0100 0101 0110 011110001001 1011 1100 1101 1010 1110 1111 0 1 2 3 4 5 6 789 A D C B E F 0 1 2 3 4 5 6 789 10 11 12 13 14 15 0 1 -8 3 4 5 6 7 2 -7 -6 -5 -4 -3 -2 -1 Why one more negative than positive?
- 14. CoxSimple Data Types14 Integer Representations Math for n bits: Define 1 0 2)(2 n i i i xxUB 2 0 1 1 22)(2 n i i i n n xxxTB 01 xxx n sign bit 0=non-negative 1=negative Base 2 Base 16 Unsigned 2’s Comp. 0000 0 0 0 0001 1 1 1 0010 2 2 2 0011 3 3 3 0100 4 4 4 0101 5 5 5 0110 6 6 6 0111 7 7 7 1000 8 8 -8 1001 9 9 -7 1010 A 10 -6 1011 B 11 -5 1100 C 12 -4 1101 D 13 -3 1110 E 14 -2 1111 F 15 -1
- 15. 15 Memory Layout of Records initials (2 bytes) married (1 byte) ss_number (4 bytes) • Fields are stored adjacently in memory. • Memory is allocated for records based on the order the fields are created. • Variables are aligned for easy reference. initials (2 bytes) ss_number (4 bytes) married (1 byte) Optimized for space Optimized for memory alignment 4 bytes / 32 bits 4 bytes / 32 bits