CS102B - Lesson 3
More Operators, Precedence, Conditional Statements, Basic Input/Output, Switch
Instructor: Professor Hong
## Review & Questions
## Relational & Logical Operators
## Relational & Equailty Operators Relational Operators: * <code>></code> -- greater than * <code>>=</code> -- greater than or equal to * <code><</code> -- less than * <code><=</code> -- less than or equal to Equality Operators: * <code>==</code> -- equal to; note that you use 2 = signs * <code>!=</code> -- not equal to These operators result in a boolean (true or false).
## Logical Operators: * <code>&&</code> -- logical and * <code>||</code> -- logical or * These operators also result in a boolean (true or false). * For numeric types, 0 is equivalent to false and any non-zero is true. * These are different from bitwise operations which we will learn later.
## The Unary Operator '!' * Negates the boolean * <code>!0</code> -- true * <code>!1</code> -- false * <code>!100</code> -- false * <code>!(5 < 2)</code> -- true * <code>!((5 < 2) || !(3 < 1))</code> -- false
## Bitwise Operators
## Bitwise Operators * <code>&</code> -- bitwise AND * <code>|</code> -- bitwise inclusive OR * <code>^</code> -- bitwise exclusive OR * <code><<</code> -- left shift * <code>>></code> -- right shift * <code>~</code> -- one's complement (unary)
## Bitwise Operators Example ``` #include <stdio.h> int main() { printf("5 & 4 = %d\n", 5 & 4); printf("5 | 4 = %d\n", 5 | 4); printf("5 ^ 4 = %d\n", 5 ^ 4); printf("5 << 2 = %d\n", 5 << 2); printf("12 >> 2 = %d\n", 12 >> 2); printf("~5 = %d\n", ~5); // Note 2's complement // 5 is 0000...0101 // Doing on's complement, we have // ~5 is 1111...1010 // which is MIN+sum(2^n) where n excludes n=0 and n=2 // Or simpler: -8 + 0 + 2 + 0 return 0; } ```
## Assignment Operators
## Assignment Operators * <code>i = i + 2</code> is equivalent to <code>i += 2</code> * <code>i = i - 2</code> is equivalent to <code>i -= 2</code> * <code>expr1 = (expr1) op (expr2)</code> is equivalent to <code>expr1 op= expr2</code> * Also works for: <code>* / % << >> & ^ |</code> * Commonly used in loops
## Precedence
## Precedence & Associativity Operators <img data-src="https://github.com/hong3cooper/ECE160B-Fall2018-Lesson2/blob/master/precedence.png?raw=true">
## Conditional Statements
## If Statements ``` if (a > b) { z = a; // do something } ``` * Example ``` #include <stdio.h> int main() { int a = 0; int b = 5; if (a < b) { printf("a is less than b\n"); } return 0; } ```
## If-Else Statements ``` if (a > b) { z = a; // do something } else { z = b; // do something else } ``` or ``` expr1 ? expr 2 : expr 3 ```
## If-Else Statement Example ``` #include <stdio.h> int main() { int a = 7; int b = 5; if (a < b) { printf("a is less than b\n"); } else { printf("a is greater than or equal to b\n"); } return 0; } ```
## If-Else If-Else Statements ``` if (a > b) { z = a; // do something } else if (a > c) { z = c; // do something } else { z = b; // do something else } ```
## If-Else If-Else Statement Example ``` #include <stdio.h> int main() { int a = 1; int b = 2; int c = 3; if (a < b) { printf("a is less than b\n"); } else if(a < c) { printf("a is less than c and greater than or equal to b\n"); } else { printf("a is greater than or equal to b and a is greater than or equal to c\n"); } return 0; } ```
## Basic Input/Output
## getchar * gets **one** character from the command line ``` #include <stdio.h> int main() { char c = getchar(); putchar(c); printf("%c", c); return 0; } ```