Examples and debugging
Let's now explore some practical examples to better understand the concepts we've covered in the last chapter. Open VS Code or go to C/C++ Shell in your browser to execute the following programs. To debug, see below.
Arithmetic Operators​
arithmetic_operators.c
#include <stdio.h>
int main() {
// Examples of arithmetic operators
float a = 10 + 1;
float b = 20 - 3;
float c = 3 * 2;
float d = 10 / 3; // Integer division
float e = 10 / 3.0; // Floating-point division
float f = 10 % 3; // Remainder of integer division
float g = 10 / (float)3; // Floating-point division (with cast)
printf("a = %.1f\n", a);
printf("b = %.1f\n", b);
printf("c = %.1f\n", c);
printf("d = %.1f\n", d);
printf("e = %.2f\n", e);
printf("f = %.1f\n", f);
printf("g = %.2f\n", g);
return 0;
}
a = 11.0
b = 17.0
c = 6.0
d = 3.0
e = 3.33
f = 1.0
g = 3.33
Relational and Logical Operators​
relational_logical_operators.c
#include <stdio.h>
int main() {
// Examples of relational operators
int a = 3 < 4; // Reads as a = (3 < 4)
int b = 3 >= 4;
int c = 2 == 1;
int d = 1 == 1;
// Examples of logical operators
int e = !(2 > 3);
int f = (1 != 2) && (3 == 4);
int g = (1 != 2) || (3 == 4);
printf("3 >= 4: %d\n", b);
printf("2 == 1: %d\n", c);
printf("1 == 1: %d\n", d);
printf("!(2 > 3): %d\n", e);
printf("(1 != 2) && (3 == 4): %d\n", f);
printf("(1 != 2) || (3 == 4): %d\n", g);
return 0;
}
3 >= 4: 0
2 == 1: 0
1 == 1: 1
!(2 > 3): 1
(1 != 2) && (3 == 4): 0
(1 != 2) || (3 == 4): 1
Operator Precedence​
operator_precedence.c
#include <stdio.h>
int main() {
// Try to interpret these expressions and verify your expectations
float a = 3 * 2 - 1;
float b = 7 / 2 * 2;
float c = 7 / 2.0 * 2;
float d = 7 / 2 * 2.0;
float e = 13 % 2 == 1;
float f = 1 <= 3 && 2 <= 4;
// Some examples to avoid
float g = 2 <= 3 <= 4; // Not what you might expect!
float h = (2 != 3) * 4; // Mixing comparison and multiplication
float i = 1 < 3 == 2 < 4; // Confusing chain of comparisons
printf("a = %.1f\n", a);
printf("b = %.1f\n", b);
printf("c = %.1f\n", c);
printf("d = %.1f\n", d);
printf("e = %.1f\n", e);
printf("f = %.1f\n", f);
printf("g = %.1f\n", g); // Results might be unexpected
printf("h = %.1f\n", h);
printf("i = %.1f\n", i); // Results might be unexpected
return 0;
}
a = 5.0
b = 6.0
c = 7.0
d = 2.0
e = 1.0
f = 1.0
g = 1.0
h = 4.0
i = 1.0
Assignment and Increment/Decrement​
assignment_increments.c
#include <stdio.h>
int main() {
// The assignment operator writes a value to a variable
int a = 10;
a = a + 2;
printf("a = %d\n", a); // Output: 12
// Increment and decrement have two notations
int b = a++; // Postfix notation (denotes the value before increment)
printf("b = %d, a = %d\n", b, a); // Output: b = 12, a = 13
int c = ++a; // Prefix notation (denotes the value after increment)
printf("c = %d, a = %d\n", c, a); // Output: c = 14, a = 14
// Some operators have a compact notation when combined with assignment
a += 2; // Equivalent to: a = a + 2
printf("a += 2: %d\n", a); // Output: 16
a -= 2; // Equivalent to: a = a - 2
printf("a -= 2: %d\n", a); // Output: 14
// The assignment operator is itself an expression
int d = (a = 2 * a);
printf("d = (a = 2 * a): d = %d, a = %d\n", d, a); // Output: d = 28, a = 28
int e = a /= 2;
printf("e = a /= 2: e = %d, a = %d\n", e, a); // Output: e = 14, a = 14
return 0;
}
a = 12
b = 12, a = 13
c = 14, a = 14
a += 2: 16
a -= 2: 14
d = (a = 2 * a): d = 28, a = 28
e = a /= 2: e = 14, a = 14
Integer Types and Representation​
integer_types.c
#include <stdio.h>
int main() {
// Variable assignment (integer types)
int a = 10;
short int b = 2;
long int c = 1000;
long long int d = 1234;
// Different representation capacities (value ranges)
short e = 32767; // Maximum value for short
int f = 2147483647; // Maximum value for int (32-bit)
long g = 2147483647L; // Long literal with 'L' suffix
long long h = 9223372036854775807LL; // Long long literal with 'LL' suffix
printf("int: %d\n", a);
printf("short int: %hd\n", b);
printf("long int: %ld\n", c);
printf("long long int: %lld\n", d);
printf("max short: %hd\n", e);
printf("max int: %d\n", f);
printf("long value: %ld\n", g);
printf("long long value: %lld\n", h);
return 0;
}
int: 10
short int: 2
long int: 1000
long long int: 1234
max short: 32767
max int: 2147483647
long value: 2147483647
long long value: 9223372036854775807
Debugging Expressions in C​
Debugging is a crucial skill when working with expressions. Visual Studio Code makes it easy to observe how variables change as your program executes. You can read the detailed guide to debugging in VS Code on Debug code with Visual Studio Code, while here you'll find a short explanation on how to do it.
We'll use the following program, to also understand operator precedence:
debug_arithmetic.c
#include <stdio.h>
int main() {
int a = 5;
int b = 3;
int result1 = a + b * 2; // Set a breakpoint here
int result2 = (a + b) * 2;
printf("result1 = %d\n", result1);
printf("result2 = %d\n", result2);
return 0;
}
Setting up breakpoints​
- Open your C file in Visual Studio Code
- Click in the margin to the left of a line number to set a breakpoint (a red dot will appear)
- Start debugging by pressing F5 or clicking the "Run and Debug" button
Watching variables change​
- Once the program pauses at your breakpoint, observe the current values in the "Variables" panel
- Use the "Step Over" button (F10) to execute the next line
- Watch how variable values change after each operation
This technique allows you to visualize how expressions are evaluated step-by-step and helps identify any issues in your code, a very important job of software development.