Chapter 7

1. Chapter 7 Introduction to Programming in C

2. Program 6 - Solution int main() { int i, n, d; /* Counter, number of days in month, number in week */ printf("Enter the number of days in the month:"); scanf("%d" , &n); printf("Enter Starting day of week: (1=Sunday , 7=Sat.):"); scanf("%d" , &d); for (i = 1; i < d; i++) /* Move to the correct position */ printf(" "); for (i = 1; i <= n; i++) { /* Print the rest of the days */ printf("% d " , i); if (((d + i - 1) % 7) = = 0) printf("\n" ); } return 0; }

3. Integer Types • Four types of integers: • Long or short • Signed or unsigned • To declare: • short int • unsigned short int • int • unsigned int • long int • unsigned long int

4. Character Types • Characters are represented by 8 bits • ASCII: American Standard Code for Information Interchange Char Octal Dec Hex Description .... A 101 65 41 Uppercase A B 102 66 42 Uppercase B C 103 67 43 Uppercase C D 104 68 44 Uppercase D E 105 69 45 Uppercase E ..... X 130 88 58 Uppercase X Y 131 89 59 Uppercase Y Z 132 90 5a Uppercase Z [ 133 91 5b Opening square bracket \ 134 92 5c Reverse slant (Backslash) ..... ` 140 96 60 Opening single quote a 141 97 61 Lowercase a b 142 98 62 Lowercase b c 143 99 63 Lowercase c

5. Use of char type variables char ch; ch = ‘a’; ch = ‘0’; ch = ‘>’; ch = ‘A’; /* ch is now ‘A’ */ ch = ch + 1; /* ch is now ‘B’ */ for (ch = ‘A’; ch <= ‘Z’; ch++)…

6. Use of char type variables What does this do? char ch; if ((‘a’ <= ch) && (ch <= ‘z’)) ch = ch – ‘a’ + ‘A’

7. Character-handling Functions char ch; … if ((‘a’ <= ch) && (ch <= ‘z’)) ch = ch – ‘a’ + ‘A’ The code below has the same effect: char ch; … toupper(ch); Note – you have to include the file <ctype.h>

8. Reading and Writing Characters char ch; … /* Now, to scan a character use %c */ scanf(“%c”, &ch); printf(“%c”, ch); What does this do? do { scanf(“%c”, &ch); } while (ch != ‘\n’);

9. Reading and Writing Characters C provides a way to read and write characters: char ch; … ch = getchar(); /* Reads a single character */ putchar(ch); /* Writes a single character */ We can rewrite this code using putchar() do { scanf(“%c”, &ch); } while (ch != ‘\n’);

10. Reading and Writing Characters We can rewrite this code using putchar() do { scanf(“%c”, &ch); } while (ch != ‘\n’); do { ch = getchar(); } while (ch != ‘\n’); Or even: while ((ch = getchar()) != ‘\n’) ;

11. Reading and Writing Characters We can rewrite this: while ((ch = getchar()) != ‘\n’) ; In an even simpler form: while (getchar() != ‘\n’) ; Also, can test for another character. What does this do? while (getchar() != ‘Z’) ;

12. Reading and Writing Characters /* Determines the length of a message */ #include <stdio.h> main() { char ch; int len = 0; printf("Enter a message: "); ch = getchar(); while (ch != '\n') { len++; ch = getchar(); } printf("Your message was %d character(s) long.\n", len); return 0; }

13. Reading and Writing Characters /* Determines the length of a message */ #include <stdio.h> main() { int len = 0; printf("Enter a message: "); while (getchar() != '\n') len++; printf("Your message was %d character(s) long.\n", len); return 0; }

14. Reading and Writing Characters /* Determines the length of a message */ #include <stdio.h> main() { int len = 0; printf("Enter a message: "); while (getchar() != '\n') len++; printf("Your message was %d character(s) long.\n", len); return 0; }

15. sizeof Operator The sizeof operator allows the program to determine how many bytes of memory are required to store values of a particular data type. Format: sizeof (type) Example: printf("the int is %d\n", sizeof(int)); … sizeof (char) is always 1 sizeof(int) is 4 sizeof(double) is 8

16. Type Conversions Type conversion: convert a unit of data from one type to another Automatic in some cases: • Add an int to a long int: compiler converts the int to a long int • Add an int to a float: compiler converts the int to a float “Implicit conversions” – compiler handles automatically “Explicit conversions” – use the cast operator

17. Implicit Conversions • When the operands in an arithmetic or logical expression don’t have the same type • When the type of the expression on the right side of an assignment doesn’t match that on the left side • When the type of an argument in a function call doesn’t match the type of the corresponding parameter • When the type of the expression in the return statement doesn’t match the function’s return type

18. Examples – Arithmetic Conversions char c; long int l; short int s; unsigned long int ul; int i; float f; unsigned int u; double d; long double ld; i = i + c; /* c is converted to int */ i = i + s; /* s is converted to int */ u = u + i; /* i is converted to unsigned int */ l = l + u; /* u is converted to long int */ i = i + c; /* c is converted to int */ ul = ul + l; /* l is converted to unsigned long int */ f = f + ul; /* ul is converted to float */ d = d + f; /* f is converted to double */ ld = ld + d; /* d is converted to long double */

19. Examples – Conversions During Assignment char c; int i; float f; double d; i = c; /* c is converted to int */ f = i; /* i is converted to float */ d = f; /* f is converted to double */

20. Some BAD Ideas – DON’T DO THIS char c; int i; float f; double d; i = 57.33; /* NO! */ i = 1.0e20; /* NO, NO!! */ f = 1.0e100; /* Nope. */ c = 10000; /* Won’t work */

21. Type Casting C allows us to “cast” an expression. (type) expression; For example – assume you have a float f = 100.00; And you happen to need to use it as an integer for assignment to an integer variable: i = (int) f; /* Converts f to an integer */

22. Bad News • Test Friday!!!!

23. Homework: • Page 135, #6, 16, 14, 17

24. Program 7 • Page 135, #9 • 10 Extra points for writing the program so that the assumption is dropped.