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Operators and Expressions

FTSM. Operators and Expressions. Knowledge: Know the types of basic arithmetic operators and their order of precedence Skill: Develop skills in computer arithmetic. Introduction. We use arithmetic expressions to solve most programming problems

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Operators and Expressions

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  1. FTSM Operators and Expressions Knowledge: Know the types of basic arithmetic operators and their order of precedence Skill: Develop skills in computer arithmetic Computer Science Department

  2. Introduction • We use arithmetic expressions to solve most programming problems • Arithmetic expressions comprise of operators and operands • There are rules for writing and evaluating arithmetic expressions TK1913-C Programming2

  3. Example: W + Z Operand Operand Operator Operator and Operand What are operator and operand? TK1913-C Programming3

  4. Operator and Operand Which is which? Operator ?? • Example: A / B Operand?? TK1913-C Programming4

  5. Addition (+) Modulus (%) Subtraction (-) Division (/) Multiplication (*) Basic Arithmetic Operators TK1913-C Programming5

  6. Basic Arithmetic Operators • Multiplication, addition and subtraction are the simplest to use • Division is easy, but some precautions need to be taken • Modulus is the one that normally confuses novices So, let’s study in detail the Division and Modulus TK1913-C Programming6

  7. Example: W / Z Integer Division • W and Z are integers Floating Division • W or Z or both are floats Division TK1913-C Programming7

  8. an integer  the result is also an integer an integer Integer Division • Example: 8 / 2 = 4 TK1913-C Programming8

  9. an integer  the result is also an integer an integer Integer Division • Example: 12 / 5 = 2 TK1913-C Programming9

  10. a float the result is a float an integer Floating Division • Example: 12.0 / 5 = 2 TK1913-C Programming10

  11. Something to ponder … What will be the answer if an integer is divided by 0? How about if one of the operands is a negative integer? TK1913-C Programming11

  12. Modulus • It returns the remainder that occurs after performing the division of 2 operands • Rule: Operands must be integers TK1913-C Programming12

  13. the result is the remainder of 12/5 an integer result remainder an integer Modulus • Example: 12 % 5 = 2 2 5 12 10 2 TK1913-C Programming13

  14. the result is the remainder of 7/3 an integer result remainder an integer Modulus • Example: 7 % 3 = 1 2 3 7 6 1 TK1913-C Programming14

  15. a float INVALID! an integer Modulus • Example: 12.0 % 3 = ?? TK1913-C Programming15

  16. Something to ponder … The earlier expressions contain only one operator at a time. What if the expression contains more than one operator? TK1913-C Programming16

  17. Arithmetic Expression • An expression may contain 2 or more arithmetic operators • Main issue: ORDER OF PRECEDENCE TK1913-C Programming17

  18. Arithmetic Expression • Examples: 5 + 6 = 11 5 + 6 * 2 = 17 = 22 or 17? 2.5 + 6 – 2 * 2 = ?? = ?? 12 / 6.0 – 2 * 2 TK1913-C Programming18

  19. Arithmetic Expression Order of Precedence: High:* / % Low:+ - All operators have a precedence level. High precedence level operators are evaluated before lower ones. Operators of the same precedence level are evaluated from left to right TK1913-C Programming19

  20. Example: 2.5 + 6 – 2 * 2 = 2.5 + 6 – 2 * 2 = 4.5 2.5 + 6 – 4 8.5 – 4 4.5 Arithmetic Expression • Example: 2.5 + 6 – 2 * 2 = ?? 2.5 + 6 – 2 * 2 = 2.5 + 6 – 4 8.5 – 4 4.5 TK1913-C Programming20

  21. Try it! • Example: 12 + 6.0 – 2 * 2 = ?? What’s the answer?? TK1913-C Programming21

  22. Arithmetic Expression • All expressions in parentheses (brackets) must be evaluated prior to values outside brackets • Nested parenthesized expressions must be evaluated from the inside out, with the innermost expression evaluated first • Example: ( 9 – ( 3 + 2 ) ) * 3 = ?? TK1913-C Programming22

  23. Arithmetic Expression • Example: • ( 9 – ( 3 + 2 ) ) * 3 = ??  ( 9 – ( 3 + 2 ) ) * 3 = 12 – 5 12 4 TK1913-C Programming23

  24. Assignment Statement There are 3 types of assignment: • Simple • Multiple • Shorthand TK1913-C Programming24

  25. Don’t forget the semicolon !! Simple Assignment Syntax: variable = expression ; TK1913-C Programming25

  26. Buying price: 10.00 Discount rate: 0.25 For buying price RM10.00 and discount rate 0.25 The total price is RM7.50 _ Buying price: 10.00 Discount rate: _ Buying price: 10.00 Discount rate: 0.25 _ Buying price: 10.00 _ Buying price: 10.00 Discount rate: 0.25 For buying price RM10.00 and discount rate 0.25 _ Buying price: _ price 10.00 ?? ?? discount 0.25 total ?? Simple Assignment • Example: • #include <stdio.h> • void main( ) { • float price, discount, total; • printf(“Buying price : “); • scanf(“%f”, &price); • printf(“\nDiscount rate : “); • scanf(“%f”, &discount); • total = price – (price * discount); • printf(“\nFor buying price RM%.2f and discount rate %.2f\n”, price, discount); • printf(“The total price is RM%.2f\n”, total); • } 7.50 TK1913-C Programming26

  27. Don’t forget the semicolon !! Multiple Assignment Syntax: variable = variable = expression ; TK1913-C Programming27

  28. number ?? 0 ?? 0 total start_x ?? 100.0 start_y ?? 100.0 Multiple Assignment • Example: • int number, total; • float start_x, start_y; • . . . • number = total = 0; • start_x = start_y = 100.0; TK1913-C Programming28

  29. Shorthand Assignment Syntax: variableX = variableX op expression ; variableX op= expression; TK1913-C Programming29

  30. 15 num Shorthand Assignment Whenever the expression on the right contains the variable on the left (to which the value is assigned) • Example: • num = num + 5; 20 15 + 5 20 TK1913-C Programming30

  31. shorthand assignment operator Shorthand Assignment Expressions can also be stated using shorthand assignment operators • Example: • num += 5; similar to num = num + 5 Shorthand assignment operators have the lowest order of precedence – the last one to be evaluated TK1913-C Programming31

  32. Shorthand Assignment TK1913-C Programming32

  33. 100.00 8 5.00 pay hour rate 180.00 Shorthand Assignment • Example: • pay += hour * rate * 2 similar to pay = pay + (hour * rate * 2) • pay + (hour * rate * 2)  pay + (8 * 5.00 * 2)  100.00 + 80.00  180.00 TK1913-C Programming33

  34. Assignment by Value Every assignment expression has a value • Example: • Expression 1: a = 1; • Expression 2: x = y = 0; • Expression 3: p = 12; • p = 0; • Example: • int a, x, y, p; • Line 1: a=1; • Line 2: x = y = 0; • Line 3: p = 12; • Line 4: p = p +3; • Line 5: q = p = p + x; TK1913-C Programming34

  35. Relational Operators TK1913-C Programming35

  36. Mantic/Logical Operators SymbolDescription && AND || OR ! NOT TK1913-C Programming36

  37. a b c d 2 5 15 17 Compound Statement Arithmetic, relational and mantic operators can be integrated/combined in one expression • Example: • ! ( c > a ) • ! ( 15 > 2 )  ! ( 1 )  0 TK1913-C Programming37

  38. a b c d 2 5 15 17 Compound Statement • Example: • (a >= 1) && (b == 5) • ( 2 >= 1 ) && ( b == 5 ) • 1 && ( b == 5 ) • 1 && ( 5 == 5 ) • 1 && 1 • 1 TK1913-C Programming38

  39. d a b c 2 5 15 17 Compound Statement • Example: • (c >= ( b * 3 ) ) || (a == 3) • ( c >= ( 5 * 3 ) ) || ( a == 3) • ( 15 >= 15 ) || ( a == 3) • 1 || ( a == 3 ) • 1 || ( 2 == 3 ) • 1 || 0 • 1 TK1913-C Programming39

  40. d a b c 2 5 15 17 Compound Statement • Example: • ! ( ( a < b ) || ( c > d ) ) • ! ( ( 2 < 5 ) || ( c > d ) ) • ! ( 1 || ( c > d ) ) • ! ( 1 || ( 15 > 17 ) ) • ! ( 1 || 0 ) • ! 1 • 0 TK1913-C Programming40

  41. Increment and Decrement This operation contains only one operand, that is, the operand which value will be incremented/ decremented TK1913-C Programming41

  42. num ?? Increment and Decrement • Example: • int num; • printf(“Key-in a number: “); • scanf(“%d”, &num); • printf(“Value before being incremented: %d\n”, num); • num++; • printf(“Value after being incremented: %d”, num); 26 27 Key-in a number: 26 Value before being incremented: 26 _ Key-in a number: 26 Value before being incremented: 26 Value after being incremented: 27 _ Key-in a number: _ Key-in a number: 26 _ TK1913-C Programming42

  43. Prefix and Postfix Increment and Decrement operators can be either in prefix or postfix forms TK1913-C Programming43

  44. 5 ?? i j Prefix and Postfix • Example: • j = i++ - 2 similar to j = i – 2; i = i + 1; 6 3 TK1913-C Programming44

  45. 5 ?? i j Prefix and Postfix • Example: • j = ++i - 2 similar to i = i + 1; j = i – 2; 6 4 TK1913-C Programming45

  46. 10 x ?? y 10.000000 Coersion Coersion is used to compute a value that is equivalent to its operand’s value (based on the stated data type) • Example: • int x = 10; • float y; • y = (float) x; • ( float ) 10 • 10.000000 TK1913-C Programming46

  47. 15 total 2 number ?? 7.000000 average Coersion • Example: • int total, number; • float average; • … • average = total / number; • 15 / 2 • 7 TK1913-C Programming47

  48. 15 total 2 number ?? 7.500000 average Coersion • Example: • int total, number; • float average; • … • average = (float) total / number; • 15.000000 / 2 • 7.500000 TK1913-C Programming48

  49. Yes !! That’s all? What’s next??? CONTROL STRUCTURE: SELECTION on the way … End of Lecture 6 TK1913-C Programming49

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