Introduction to C Programming
Branching
Edgar SIMO-SERRA
Last class summary
- Learned how to use floating point (
double) - Learned about implicit and explicit casting
Class Objectives
- Branching
- How to use conditional statements with logical operators
Branching
- Allow running different code depending on conditional statements
- Extremely useful and widely used
if (CONDITIONAL1) { do_something(); } else if (CONDITIONAL2) { do_something_else(); } else { do_something_completely_different(); }
Conditional statements
- Allow to evaluate conditions as either 1 (true) or 0 (false)
- Can be used to compare variables or expressions of arbitrary complexity
- Two types of operators:
- Relational operators
- Logical operators
Relational operators
a==b: a is equal to bea!=b: a is not equal to ba<b: a is smaller than ba>b: a is bigger than ba<=b: a is smaller or equal to ba>=b: a is bigger or equal to b
Relational operators (example)
int my_grade = 70;
if (my_grade < 50) {
printf( "failed the class\n" );
} else if (my_grade <= 99) {
printf( "passed the class\n" );
} else if (my_grade == 100) {
printf( "got an A+!\n" );
}- Do not confuse
=and==
Logical operators
!c: not condition ca && b: condition a and condition ba || b: condition a or condition b
Logical operators examples
int temperature = 30;
int rain = 1;
if ((rain==1) || (temperature < 20)) {
wear_sweater();
} else if ((temperature > 30) && (rain==0)) {
wear_tshirt();
} else {
wear_random();
}Switch Statement
int my_variable = 3;
switch (my_variable) {
case 1:
do_something(); break;
case 3:
do_something_else(); break;
default:
do_nothing(); break;
}Exercise 1
- Have the user input three number values
- Print the three number values in descending order
- Example: “5, 3, 8” should become “8, 5, 3”
- Additionally, print whether two or three of the numbers are the same
#include <stdio.h> int main (void) { /* Put code here. */ return 0; }
Exercise 2
- Print the real solutions of
ax2+bx+c=0- One real solution if
b2−4ac=0 - Zero real solutions if
b2−4ac<0 - Otherwise two:
x=−b±√b2−4ac2a#include <stdio.h> #include <math.h> int main (void) { /* Code missing. You can calculate the square root with "sqrt( double )" */ return 0; } - Use
-lmwhen compiling with gcc
- One real solution if
Exercise 2 (hand-in)
- Make sure your code compiles without warnings
-W -Wall -Wextra -Wconversion - Check to make sure your code works:
3x2+3x+3=0has no real solutions2x2+4x+2=0has one solutionsx=−12x2+4x+1=0has two solutionsx=−1.7071andx=−0.29289
- Please hand in this exercise through Moodle
Exercise 3
- Implement a simple single player blackjack game where at first:
- The player gets two cards (
pick_card()). - The value of the two cards gets added together.
- The player gets two cards (
- Then up to 5 times the following happens:
- The player can choose to either stay or get another card.
- If the player gets another card, it gets added together.
- If the player goes over 21, he loses.
- If the player is at 21, he wins.
Exercise 3 (base code)
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int pick_card (void) { return (rand()%10)+1; }
int main (void) {
srand(time(NULL));
/* code goes here */
return 0;
}Today’s Lesson
- Branching (if/else, switch)
- Conditional expressions (relational and logical operators)
Next Week
- Loops!
Introduction to C Programming Branching Edgar SIMO-SERRA