Simple Array Examples — 1D, 2D & Strings

🎲 Your 5 Favourite Numbers

Store numbers, find the biggest and smallest, show them all

1D int array

What this teaches: A 1D array is like a row of labelled boxes. You put one value in each box. To get a value back, you say which box number you want — that's the index. Index always starts at 0, not 1.

int nums[5] — 5 boxes, each holding one number

nums[ ]

[0]

[1]

[2]

[3]

[4]

← nums[3] = 99 is biggest

5 elements · indices 0 to 4 · nums[0] is first · nums[4] is last

favourite_numbers.c

#include <stdio.h>

int main() {
    /* Store 5 favourite numbers in an array */
    int nums[5] = {7, 42, 13, 99, 5};
    int i, biggest, smallest;

    /* Print all numbers */
    printf("Your 5 numbers: ");
    for (i = 0; i < 5; i++)
        printf("%d  ", nums[i]);
    printf("\n");

    /* Find biggest — start assuming nums[0] is biggest */
    biggest = nums[0];
    for (i = 1; i < 5; i++) {
        if (nums[i] > biggest)
            biggest = nums[i];  /* update if we find bigger */
    }

    /* Find smallest — same idea */
    smallest = nums[0];
    for (i = 1; i < 5; i++) {
        if (nums[i] < smallest)
            smallest = nums[i];
    }

    /* Print result */
    printf("Biggest  : %d\n", biggest);
    printf("Smallest : %d\n", smallest);
    printf("Total    : ");

    int total = 0;
    for (i = 0; i < 5; i++) total += nums[i];
    printf("%d\n", total);

    return 0;
}

output

result

Your 5 numbers: 7  42  13  99  5
Biggest  : 99
Smallest : 5
Total    : 166

Key idea: To find the biggest, you start by assuming the first element nums[0] is the biggest. Then you walk through the rest. Every time you find something bigger, you update your answer. This single-pass technique works for any array of any size.

example 2

🌡️ Weekly Temperature Diary

7 days of temperatures — average, hottest day, count days above 30°C

1D float array

What this teaches: Arrays are perfect for repeating measurements — one entry per day, per student, per product. A float array stores decimal numbers. float temp[7] gives you exactly 7 slots, one for each day of the week.

float temp[7] — one slot per day of the week

temp[ ]

28.5

Mon[0]

31.2

Tue[1]

38.0

Wed[2]

35.5

Thu[3]

29.0

Fri[4]

26.3

Sat[5]

27.8

Sun[6]

Wednesday (index 2) is the hottest — 38.0°C highlighted

temperature_diary.c

#include <stdio.h>

int main() {
    char days[7][4] = {
        "Mon", "Tue", "Wed", "Thu",
        "Fri", "Sat", "Sun"
    };
    float temp[7] = {28.5, 31.2, 38.0, 35.5,
                      29.0, 26.3, 27.8};
    int   i, hotDay = 0, hotCount = 0;
    float total = 0;

    /* Print diary */
    printf("Day   Temp   Comment\n");
    printf("----  -----  ----------\n");
    for (i = 0; i < 7; i++) {
        printf("%-4s  %5.1f  ", days[i], temp[i]);
        if      (temp[i] >= 35) printf("Very hot!\n");
        else if (temp[i] >= 30) printf("Hot\n");
        else                     printf("Pleasant\n");

        total += temp[i];
        if (temp[i] > temp[hotDay]) hotDay = i;
        if (temp[i] > 30) hotCount++;
    }

    printf("\nWeek average : %.1f C\n", total / 7);
    printf("Hottest day  : %s (%.1f C)\n",
           days[hotDay], temp[hotDay]);
    printf("Days over 30C: %d\n", hotCount);

    return 0;
}

output

result

Day   Temp   Comment
----  -----  ----------
Mon    28.5  Pleasant
Tue    31.2  Hot
Wed    38.0  Very hot!
Thu    35.5  Very hot!
Fri    29.0  Pleasant
Sat    26.3  Pleasant
Sun    27.8  Pleasant

Week average : 30.9 C
Hottest day  : Wed (38.0 C)
Days over 30C: 3

Two arrays, same index: days[i] and temp[i] always refer to the same day. Index 2 gives "Wed" AND 38.0 — they are linked by the shared index. This is called a parallel array — the most natural way to store related data in C.

example 3

🪑 Classroom Seating Chart

3 rows × 4 seats — mark occupied seats, count free seats, show map

2D int array

What this teaches: A 2D array is like a grid. int seat[3][4] means 3 rows and 4 columns — like a classroom. The first index picks the row, the second picks the seat in that row. 1 = occupied, 0 = free.

int seat[3][4] — 3 rows × 4 seats per row = 12 seats total

—

Seat 1

Seat 2

Seat 3

Seat 4

Row 1

Row 2

Row 3

= Occupied
= Free
free seats in green

seating_chart.c

#include <stdio.h>

int main() {
    /* 1 = occupied, 0 = free */
    int seat[3][4] = {
        {1, 1, 0, 1},   /* row 0: seat 3 is free */
        {0, 1, 1, 0},   /* row 1: seats 1 and 4 are free */
        {1, 0, 0, 1}    /* row 2: seats 2 and 3 are free */
    };
    int i, j, freeCount = 0;

    /* Print the seating map */
    printf("CLASSROOM SEATING MAP\n");
    printf("       S1   S2   S3   S4\n");
    printf("       ---- ---- ---- ----\n");

    for (i = 0; i < 3; i++) {
        printf("Row %d: ", i + 1);
        for (j = 0; j < 4; j++) {
            if (seat[i][j] == 1)
                printf(" [X] ");   /* occupied */
            else {
                printf(" [ ] ");   /* free */
                freeCount++;
            }
        }
        printf("\n");
    }

    printf("\n[X] = Taken   [ ] = Free\n");
    printf("Free seats : %d\n", freeCount);
    printf("Taken seats: %d\n", 12 - freeCount);

    /* Ask which seat they want */
    int r, s;
    printf("\nEnter row (1-3) and seat (1-4): ");
    scanf("%d %d", &r, &s);
    r--; s--;  /* convert to 0-based */

    if (seat[r][s] == 0) {
        seat[r][s] = 1;
        printf("Seat booked! Enjoy class.\n");
    } else {
        printf("Sorry, that seat is taken!\n");
    }

    return 0;
}

output

result

CLASSROOM SEATING MAP
       S1   S2   S3   S4
       ---- ---- ---- ----
Row 1:  [X]  [X]  [ ]  [X]
Row 2:  [ ]  [X]  [X]  [ ]
Row 3:  [X]  [ ]  [ ]  [X]

[X] = Taken   [ ] = Free
Free seats : 5
Taken seats: 7

Enter row (1-3) and seat (1-4): 2 1
Seat booked! Enjoy class.

Two indices, two directions: seat[i][j] — i picks the row, j picks the column. The nested loop visits every single cell. Outer loop walks rows, inner loop walks across each row. This is the core 2D array pattern.

example 4

✏️ Your Name — Character by Character

A string is a char array — count letters, print reversed, find vowels

1D char array (string)

What this teaches: In C, a string is just a char array that ends with a special invisible character '\0' (called the null terminator). You can access any letter the same way you access any array element — name[0] is the first letter, name[1] is the second, and so on.

char name[] = "Ananta" — stored as individual characters + '\0' at end

name[ ]

'A'

[0]

'n'

[1]

'a'

[2]

'n'

[3]

't'

[4]

'a'

[5]

'\0'

[6]

null end

Yellow = vowels  ·  '\0' at index 6 marks end of string  ·  strlen = 6

name_game.c

#include <stdio.h>
#include <string.h>

int main() {
    char name[20];
    int  i, len, vowels = 0, consonants = 0;

    printf("Enter your name: ");
    scanf("%s", name);

    len = strlen(name);   /* count characters */

    /* Print name letter by letter with position */
    printf("\nYour name has %d letters:\n", len);
    for (i = 0; i < len; i++)
        printf("  Letter %d : %c\n", i + 1, name[i]);

    /* Count vowels and consonants */
    for (i = 0; i < len; i++) {
        char c = name[i];
        if (c=='a'||c=='e'||c=='i'||c=='o'||c=='u'||
            c=='A'||c=='E'||c=='I'||c=='O'||c=='U')
            vowels++;
        else
            consonants++;
    }

    /* Print name reversed */
    printf("\nReversed    : ");
    for (i = len - 1; i >= 0; i--)
        printf("%c", name[i]);

    printf("\nVowels      : %d\n", vowels);
    printf("Consonants  : %d\n", consonants);

    /* First and last letter */
    printf("First letter: %c\n", name[0]);
    printf("Last  letter: %c\n", name[len - 1]);

    return 0;
}

output

result

Enter your name: Ananta

Your name has 6 letters:
  Letter 1 : A
  Letter 2 : n
  Letter 3 : a
  Letter 4 : n
  Letter 5 : t
  Letter 6 : a

Reversed    : atnanA
Vowels      : 4
Consonants  : 2
First letter: A
Last  letter: a

To reverse a string you start from the last index (len-1) and count down to 0. That's it — just loop backwards. No extra array needed. strlen() counts the characters and does NOT count the invisible '\0' at the end.

example 5

📋 Class Name List — Roll Call

Store 5 student names, take roll call, find a name, sort alphabetically

2D char array (strings)

What this teaches: A char names[5][20] is an array of strings — 5 rows, each holding a name up to 19 characters. Each row is one string. names[0] is the first name, names[4] is the last. Use strcmp() to compare strings, never ==.

char names[5][20] — each row is one student name

names[0]

'A'

'n'

't'

'a'

'\0'

← "Anta"

names[1]

'P'

'r'

'i'

'y'

'a'

'\0'

← "Priya"

names[2]

'R'

'a'

'h'

'u'

'l'

'\0'

← "Rahul"

Each row = one name  ·  Red '\0' marks end of each string  ·  Max 19 chars per name

class_namelist.c

#include <stdio.h>
#include <string.h>

int main() {
    char names[5][20] = {
        "Priya", "Ananta", "Sneha", "Rahul", "Vikram"
    };
    int  present[5] = {1, 1, 0, 1, 1}; /* 1=here 0=absent */
    int  i, j, found;
    char search[20], temp[20];

    /* ── Roll call ──────────────────────────────── */
    printf("=== ROLL CALL ===\n");
    for (i = 0; i < 5; i++) {
        printf("%d. %-10s  %s\n", i+1, names[i],
               present[i] ? "Present" : "ABSENT");
    }

    /* ── Count present and absent ───────────────── */
    int presentCount = 0;
    for (i = 0; i < 5; i++)
        if (present[i]) presentCount++;
    printf("\nPresent: %d   Absent: %d\n",
           presentCount, 5 - presentCount);

    /* ── Search for a name ──────────────────────── */
    printf("\nSearch name: ");
    scanf("%s", search);
    found = -1;
    for (i = 0; i < 5; i++) {
        if (strcmp(names[i], search) == 0) {
            found = i; break;
        }
    }
    if (found != -1)
        printf("%s is roll number %d — %s\n",
               search, found+1,
               present[found] ? "Present" : "Absent");
    else
        printf("%s not found in class.\n", search);

    /* ── Sort names alphabetically (bubble sort) ── */
    for (i = 0; i < 4; i++)
        for (j = 0; j < 4 - i; j++)
            if (strcmp(names[j], names[j+1]) > 0) {
                strcpy(temp,      names[j]);
                strcpy(names[j],  names[j+1]);
                strcpy(names[j+1], temp);
            }

    printf("\nAlphabetical order:\n");
    for (i = 0; i < 5; i++)
        printf("%d. %s\n", i+1, names[i]);

    return 0;
}

output

result

=== ROLL CALL ===
1. Priya       Present
2. Ananta      Present
3. Sneha       ABSENT
4. Rahul       Present
5. Vikram      Present

Present: 4   Absent: 1

Search name: Sneha
Sneha is roll number 3 — Absent

Alphabetical order:
1. Ananta
2. Priya
3. Rahul
4. Sneha
5. Vikram

Three things to remember about string arrays:
1. char names[5][20] — first number is how many strings, second is max length of each
2. Always use strcmp(a, b) == 0 to check if two strings are equal — never ==
3. Use strcpy(dest, src) to copy a string — never dest = src

checklist

Ex 1 — A 1D array stores values in numbered boxes starting at index 0
Ex 1 — To find biggest: start with nums[0], replace whenever you find something larger
Ex 2 — Parallel arrays: same index links two related arrays (days[i] + temp[i])
Ex 3 — 2D array: first index = row, second index = column, nested loops visit all cells
Ex 4 — A string is a char array ending in '\0' — access each letter with name[i]
Ex 4 — strlen() counts characters but does NOT count '\0'
Ex 5 — char names[5][20] stores 5 strings, each up to 19 characters long
Ex 5 — Always use strcmp() to compare strings, strcpy() to copy strings

Simple ArrayExamples

int nums[5] — 5 boxes, each holding one number

float temp[7] — one slot per day of the week

int seat[3][4] — 3 rows × 4 seats per row = 12 seats total

char name[] = "Ananta" — stored as individual characters + '\0' at end

char names[5][20] — each row is one student name

Simple Array
Examples