C Programming A Modern Approach

1. K. N. King, C ProgrammingA Modern Approach, W. W. Norton & Company, 1996. C ProgrammingA Modern Approach

2. Note About Coverage • This class has only part of the semester dedicated to C • You already know Java, which has similar syntax • You should be able to read the book quickly

3. Similarities of C to Java • /* Comments */ • Variable declarations • If / else statements • For loops • While loops • Function definitions (like methods)‏ • Main function starts program

4. Differences between C and Java • C does not have objects • There are “struct”ures • But data are not tied to methods • C is a functional programming language • C allows pointer manipulation • Input / Output with C • Output with printf function • Input with scanf function

5. Efficiency Limited amount of memory Fast Portability Compilers are small and easily written C: UNIX and ANSI/ISO standard Power Flexibility Standard library Input/output, string handling, storage allocation, etc. Integration with UNIX C Strengths

6. Can be error-prone Flexibility C compiler doesn’t detect many programming mistakes Pitfalls Can be difficult to understand Some features are easier to be misused Flexibility Can be difficult to modify No modules C Weakness

7. Compiling and Linking

8. C is case-sensitive Compiler remembers only first 31 characters Type Should be declared int height, length, width; Declarations must precede the statements. The value should be assigned before using the variable in computations: height = 8; length = 12; width = 5; int volume = height * length * width; Variables and Assignments

9. Macro definition: #define SCALE_FACTOR (5.0/9.0) No semicolon at the end! Constants

10. printf(string, expr1, expr2,…) Format string contains both ordinary characters and conversion specifications Conversion specification is a placeholder representing a value to be filled in during printing. The information after % specifies how the value is converted form its internal form(binary) to printed form (characters) Formatted Output: printf

13. Pitfalls

15. scanf(string, expr1, expr2,…) Reads input according to a particular format. Format string contains both ordinary characters and conversion specifications scanf(“%d%d%f%f”, &i, &j, &x, &y); Number of conversion specification should match number of variables. Each conversion should be appropriate for type of the variable. while (scanf (“%d”, &i)==1) { … } Formatted Input: scanf

16. For each conversion specification, tries to locate an item of appropriate type, skipping blank spaces if necessary. Reads it, stopping when it encounters the symbol that can’t belong o item. Ignores white-space characters. scanf(“%d%d%f%f”, &i, &j, &x, &y); How scanf Works

18. Simple assignment(right associative): = int i=5, j=3; int k = 5*3; i = 72.99; float f; f = 136; i = j = k = 7; f = i = 33.3; k = 1 + (j = i); Compound assignments(right associative): +=, -=, *=, /=, %= i += j += k; i += k; vs i =+ k; Assignment Operators

19. Prefix operators: ++i, --i Postfix operators: i++, i— Increment and Decrement Operators

20. Precedence and Associativity

21. a = 5; c = (b = a + 2) – (a = 1); i = 2; j = i * i ++; Any expression can be used as a statement i++; i*j -1; i + j ; /* i = j */ Sub expression Evaluation

22. Relational Operators • 0 (false) and 1 (true) • Their precedence is lower than the precedence of the arithmetic operators. • Left associative • i < j < k

23. 0 (false) and 1 (true) Their precedence is lower than the precedence of the relational operators. i < j == j < k Left associative Equality Operators

24. Logical negation: ! !expr : 1 if expr has the value 0 Right associative The same precedence as unary plus and minus Logical and: && expr1 && expr2 : 1 if both expr1 and expr2 has non-zero values Logical or: || expr1 || expr2 : 1 if either expr1 or expr2 (or both) has non-zero values Short-circuit evaluation Left associative The precedence is lower that that of the relational and equality operators Logical Operators

25. if (expression) statement if (expression) statement else statement Statement can be compound: { statements} if (i==0) vs if (i=0) if (expression) statement else if (expression) statement … else statement if … else Statement

27. if (y != 0) if (x != 0) result = x / y; else printf (“Error: y is equal to ) \n”); Use compound statement {} Compiler always match the closest unmatched if statement “Dangling else” Problem

28. expr1 ? expr2: expr3 int i, j, k; i = 1; j = 2; k = i > j ? i : j ; k = (i > 0 ? i : 0) + j ; return (i > j ? i : j); printf (“%d\n”, i > j ? i : j); Conditional Expression

29. switch ( expression ){ case constant-expression: statements … case constant-expression: statements default: statements } Controlling expression should be an integer expression (characters) Constant expression can’t contain variables or function calls. Statements do not require {}. Usually, the last statement is break. switch Statement

30. Example

31. while (expression) statement Statement can be compound: {} while (i>0) printf (“%d\n”, i--); while (i>0) { printf (“%d\n”, i); i--; } Infinite loops: while(1) Break, goto, return while Loop

32. Example scanf(“%d”, &n);

33. do statement while (expression); Statement can be compound: {} do printf (“%d\n”, i--); while (i>0) ; do { printf (“%d\n”, i); i--; } while (i>0); do Loop

34. for (expr1; expr2; expr3) statement Statement can be compound: {} expr1; while (expr2) { statement expr3; } for (i=10; i>0; i--) printf (“%d\n”, i); Infinite loop: for (;;) Comma operator: for (i=1, j=2; i+j<10; i++, j++) printf (“%d\n”, i+j); for Loop

35. Example

36. for (d=2; d<n; d++) if (n%d==0) break; if (d<n) printf (“%d is divisible by %d\n”, n,d); else printf(“%d is prime \n”,n); for (;;){ printf (“Enter a number(0 to stop): ”); scanf(“%d”,&n); if (n==0) break; printf(“%d cubed is %d\n”,n,n*n*n); } break escapes only one level of nesting. Exiting From a Loop: break

37. n = 10; sum = 0; while (n-->0){ scanf(“%d”, &i); if (i%2==0) continue; sum+=i; } Skipping the Rest of Iteration: continue

38. ; for (d=2; d<n; d++) if (n%d==0) break; for (d=2; d<n && n%d !=0 ; d++); Accidentally putting a semicolon after the parentheses in if, while or for statement ends the statement prematurely. if (i==0); printf (“Zero\n”); while (i>0); printf (“%d\n”, i--); Null statement

39. Signedness: signed (defaut), unsigned Size: short, long <limits.h> holds ranges for int types. Basic Types: Integers

40. Decimal (base 10) literals digits between 0-9, no leading zero 15, 255, 32767 Octal (base 8) literals digits between 0-7, must start with 0 017, 0377, 077777 Hexadecimal (base 16) literals digits between 0-9 and letters between A-F (a-f), must start with 0x (0X) 0xF, 0xFF, 0x7FFF Integer Constants

41. <float.h> Assume IEEE 754 standard Scientific notation: sign, an exponent, a fraction .57e2, 57, 5.7e+1, 570.0e-1 Basic Types: Floating Types

42. Character set: Latin (7 bit), ASCII (8 bit) Treats as integers unsigned (0-255) and signed (-128-127) version Some compilers use unsigned by default, the other compilers use signed by default. char ch=65; /* it’s ‘A’ now */ int i = ‘a’; /* it’s 97 */ ch++; /* it’s ‘B’ now */ if (‘a’< =ch && ch <=‘z’) ch = ch – ‘a’ + ‘A’; /* ch=toupper(ch);*/ for (ch=‘A’; ch<=‘Z’; ch++) … ch=‘a’ * ‘b’ / ‘c’ … Basic Types: char

43. ch = getchar(); putchar(ch); while ( ( ch = getchar() ) != ‘\n’ ) … while ((ch=getchar())==‘ ’); printf(“Enter an integer: ”); scanf(“%d”, &i); printf(“Enter a command: ”); command = getchar(); Read and Write char: Alternative

44. sizeof (type-name) Unsigned integer representing the number of bytes required to store a value of type-name sizeof(char) is always 1 Can be applied to constants, variables, expressions int i, j; int k= sizeof(i); /* k is assigned 2*/ k = sizeof (i + j ); sizeof Operator

45. Convert operands to the “narrowest” type that will safely accommodate both values. If the type of either operand is a floating point: float -> double - > long double Otherwise: if there are short and char operands, convert them to int, then int -> unsigned int -> long int -> unsigned long int int i= -10; unsigned int u=10; Implicit Type Conversion

46. char c = ‘A’; int ind; float f; double d; i = c; /* will get 65 */ f = i; /* will get 65.0 */ d = f; i = 824.97; /* 824 */ c= 100000000; f = 1.0e1000; Conversion During Assignment

47. (type-name) expression Unary operator float f = 3.45, frac; frac = f – (int) f; int num1=5, num2 =3; float quotient = (float) num1/ num2; int i=1000; long int i = (long int) j * j; long int i = (long int) (j * j) Explicit Type Conversion: cast

48. Celsius vs Fahrenheit table (in steps of 20F)‏ • C = (5/9)*(F-32); #include <stdio.h> int main() { int fahr, celsius, lower, upper, step; lower = 0; upper = 300; step = 20; fahr = lower; while (fahr <= upper) { celsius = 5 * (fahr - 32) / 9; printf("%d\t%d\n",fahr, celsius); fahr += step; } return 1; } • 5/9 = 0 • Integer arithmetic: 0F = 17C instead of 17.8C • %d, %3d, %6d etc for formatting integers

49. New Version Using Float #include <stdio.h> int main() { float fahr, celsius; int lower, upper, step; lower = 0; upper = 300; step = 20; fahr = lower; while (fahr <= upper) { celsius = (5.0 / 9.0) * (fahr - 32.0); printf("%3.0f %6.2f \n", fahr, celsius); fahr += step; } return 1; } • %6.2f 6 wide; 2 after decimal • 5.0/9.0 = 0.555556 • Float has 32 bits • Double has 64 bits • Long Double has 80 to 128 bits • Depends on computer

50. Version 3 with “for” loop #include <stdio.h> int main() { int fahr; for (fahr=0; fahr <= 300; fahr += 20)‏ printf("%3d %6.1f \n", fahr, (5.0 / 9.0) * (fahr – 32.0)); return 1; }