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Introduction to Conditional Statements in Programming

This lecture from ECS30 at the University of California, Davis, covers the fundamentals of conditional statements in programming, specifically focusing on decision-making processes using `if`, `else`, and conditional expressions. The concepts include logical operators (AND, OR, NOT), the structure of conditional flow control, and practical examples of comparing values and swapping variables. Additionally, the lecture explores boolean logic and the implications of different conditions in programming, providing crucial insights for problem-solving in computer science.

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Introduction to Conditional Statements in Programming

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  1. ecs30 Winter 2012:Programming and Problem Solving#07: Chapters 2~5 Dr. S. Felix Wu Computer Science Department University of California, Davis http://www.cs.ucdavis.edu/~wu/ wu@cs.ucdavis.edu ecs30 WInter 2012 Lecture #07

  2. decision F T if (condition) { <statement> <statement> (optional) } else { <statement> <statement> (optional) } <other statements> ecs30 WInter 2012 Lecture #07

  3. What is the “condition”? ecs30 WInter 2012 Lecture #06

  4. OR, AND, XOR X Y (X || Y) (X && Y) (X Y) T T T T F T F T F T F T T F T F F F F F ecs30 WInter 2012 Lecture #06

  5. Brainstorming… What is this program segment doing? Assuming: int x, y, temp; ecs30 WInter 2012 Lecture #06

  6. void Compare_and_swap(double *xp, *yp) { double temp; if (*xp > *yp) { temp = *yp; *yp = *xp; *xp = temp; } } ecs30 WInter 2012 Lecture #06

  7. ecs30 WInter 2012 Lecture #06

  8. if ((!flag) || ((y+z) >= (x-z))) { // true } else { // false } ecs30 WInter 2012 Lecture #06

  9. printf and fprintf printf("Name: %s\n", yourname); fprintf(stdout, "Name: %s\n", yourname); %./a.out > out.xyz fprintf(stderr, "Name: %s\n", yourname); ecs30 WInter 2012 Lecture #06

  10. “conditional” flow control ecs30 WInter 2012 Lecture #06

  11. ecs30 WInter 2012 Lecture #06

  12. ecs30 WInter 2012 Lecture #06

  13. Conditional Swapping Assuming: int x, y, temp; ecs30 WInter 2012 Lecture #06

  14. if ((!flag) || ((y+z) >= (x-z))) { // true } else { // false } ecs30 WInter 2012 Lecture #06

  15. T/F if (x == 0) {// TRUE} else {//FALSE} • What should be “x”? (In what ranges of x, the condition will be true?) ecs30 WInter 2012 Lecture #06

  16. T/F if (x == 1) {// TRUE} else {//FALSE} • What should be “x”? (In what ranges of x, the condition will be true?) • ONLY (x == 1) (0 for 32 bits) 00000000 00000000 00000000 00000001 ecs30 WInter 2012 Lecture #06

  17. T/F if (x == 1) {// TRUE} else {//FALSE} • What should be “x”? if (x) {// TRUE} else {//FALSE} 00000010 00010000 00000000 00000000 !(00000000 00000000 00000000 00000000) if (x = 0) {// TRUE} else {//FALSE} (00000000 00000000 00000000 00000000) Always false! ecs30 WInter 2012 Lecture #06

  18. Logical Negation if (!x) {// TRUE} else {//FALSE} • What should be the value of x? if (x == 0) {// TRUE} else {//FALSE} ecs30 WInter 2012 Lecture #06

  19. Logical/Bitwise • Logical: (if statements) • X = {false or true} {zero or otherwise} • Bitwise: we operate on every bit! 00000000 00000000 00000000 00000001 & 10101010 00000000 00000000 10101011 00000000 00000000 00000000 00000001 ecs30 WInter 2012 Lecture #06

  20. Special Symbols(Appendix C) Logical • ||, &&, >, <, >=, <=, ==, != • ! Bitwise • |, &, ^, <<, >>, ~ ecs30 WInter 2012 Lecture #06

  21. if and ? printf(“%d\n”, (x>y) ? x : y); if (x > y) { printf(“%d\n”, x); } else { printf(“%d\n”, y); } ecs30 WInter 2012 Lecture #06

  22. Brainstorming… ecs30 WInter 2012 Lecture #06

  23. Brainstorming… if ((x>= min) && (x <= max)) { // TRUE } ecs30 WInter 2012 Lecture #06

  24. Brainstorming… ecs30 WInter 2012 Lecture #06

  25. Brainstorming… if ((x < z) || (x > y)) { // TRUE } ecs30 WInter 2012 Lecture #06

  26. char class; switch(class) { case ‘B’: case ‘b’: printf(“Battleship\n”); break; case ‘C’: case ‘C’: printf(“Cruiser\n”); break; default: printf(“Unknown class %c\n”, class); } ecs30 WInter 2012 Lecture #06

  27. int class; switch(class) { case 0: case 1: printf(“Battleship\n”); break; case 2: printf(“Cruiser\n”); break; default: printf(“Unknown class %d\n”, class); } ecs30 WInter 2012 Lecture #06

  28. decision F T decision ecs30 WInter 2012 Lecture #07

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