The Symbol Dictionary: Every Sign in C and What It Says

Bob points at his screen and asks Maria what the squiggly thing does. Maria asks which squiggly thing. There are three on that line.

Neither of them can look it up, because neither knows what it is called. This lesson is the dictionary. It turns "what does the little hat thing do" into "what does the caret operator do in C", which has an answer in one search.

Keep this lesson open while you work through the rest of the track. It is a reference page, not a chapter to memorise.

Brackets and braces: four pairs, four jobs

C uses four kinds of bracket, and they are not interchangeable. Using the wrong one is the fastest way to a confusing message.

So parentheses call and group, braces hold blocks, brackets index arrays, and angle brackets do two unrelated jobs.

Arithmetic and assignment

Read = out loud as "gets", not as "equals". That one habit prevents the trap from the last lesson.

Comparison and logic

Every symbol in this table gives you a number: 1 for true, 0 for false. Example 2 below prints all six of the comparisons.

Punctuation and structure

That is the whole punctuation set. Nothing else in C is a symbol you have not now met.

The six pairs that look alike

These are the pairs that cost beginners hours. Each row is two symbols that sit next to each other on the keyboard and mean unrelated things.

Exercise 2 below is a program that uses four of these six in a row, and asks you to predict what it prints.

Escape sequences: the characters with no shape

A backslash inside a string starts an escape sequence. It is how you type a character that has no visible shape of its own, or one that would otherwise end the string.

Each escape is one character in the output, however many you typed. Counting that correctly is the brain teaser at the end.

#include <stdio.h>        /* angle brackets: a system header */

int main(void)             /* parentheses: the parameter list */
{                          /* braces: the body of main */
    int marks[3] = {90, 85, 77};   /* brackets declare, braces initialise */

    printf("%d\n", marks[0]);      /* parentheses call, brackets index */
    return 0;
}

90

#include <stdio.h>

int main(void)
{
    int a = 7;
    int b = 4;

    printf("a == b gives %d\n", a == b);
    printf("a != b gives %d\n", a != b);
    printf("a > b  gives %d\n", a > b);
    printf("a < b  gives %d\n", a < b);
    printf("a >= b gives %d\n", a >= b);
    printf("a <= b gives %d\n", a <= b);
    return 0;
}

a == b gives 0
a != b gives 1
a > b  gives 1
a < b  gives 0
a >= b gives 1
a <= b gives 0

#include <stdio.h>

int main(void)
{
    printf("Name\tMarks\n");
    printf("Zara\t92\n");
    printf("Kenji\t87\n");
    printf("She said \"well done\"\n");
    printf("Path: C:\\progsity\\bin\n");
    printf("Discount: 15%%\n");
    return 0;
}

Name	Marks
Zara	92
Kenji	87
She said "well done"
Path: C:\progsity\bin
Discount: 15%

printf('Hello\n');

char grade = "A";

printf("Path: C:\progsity\bin\n");

int total-marks = 90;

printf("a\\b\"c\n");

#include <stdio.h>

int main(void)
{
    int a, b;
    scanf("%d %d", &a, &b);

    /* Print: open-paren, a, space, plus, space, b, close-paren,
       space, asterisk, space, 2, space, equals, space, the value. */
    printf("%d\n", 0);

    return 0;
}

#include <stdio.h>

int main(void)
{
    int a = 6;
    int b = 3;
    char grade = 'A';

    printf("%d\n", a & b);
    printf("%d\n", a && b);
    printf("%c\n", grade);
    printf("%d\n", a / b);
    return 0;
}

Next you will see why a character is really a small number, and the complete table that says which number each character is.