Common array operations - Step-by-Step Execution

Concept Flow - Common array operations

Start

↓

Declare array

↓

Initialize elements

↓

Access elements by index

↓

Modify elements

↓

Traverse array with loop

↓

Perform operations (sum, search, etc.)

↓

End

This flow shows the basic steps to work with arrays: declare, initialize, access, modify, loop through, and perform operations.

Execution Sample

C

int arr[5] = {1, 2, 3, 4, 5};
int sum = 0;
for (int i = 0; i < 5; i++) {
    sum += arr[i];
}
printf("Sum: %d", sum);

This code creates an array of 5 integers, sums all elements using a loop, and prints the total.

Execution Table

Step	i	arr[i]	Condition (i<5)	Action	sum
1	0	1	True	sum = 0 + 1	1
2	1	2	True	sum = 1 + 2	3
3	2	3	True	sum = 3 + 3	6
4	3	4	True	sum = 6 + 4	10
5	4	5	True	sum = 10 + 5	15
6	5	-	False	Exit loop	15

💡 Loop ends when i reaches 5 and condition i < 5 becomes false.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	Final
i	-	0	1	2	3	4	5
sum	0	1	3	6	10	15	15
arr[i]	-	1	2	3	4	5	-

Key Moments - 3 Insights

Why does the loop stop when i equals 5, not when i is greater than 5?

Because the loop condition is i < 5, so when i becomes 5, the condition is false and the loop exits (see execution_table step 6).

Why do we use arr[i] to access elements?

Arrays store elements in order, and arr[i] accesses the element at position i (starting from 0). This is shown in the execution_table where arr[i] changes each step.

What happens if we try to access arr[5]?

Accessing arr[5] is out of bounds since valid indices are 0 to 4. This causes undefined behavior in C and should be avoided.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of sum after step 3?

A 3

B 6

C 10

D 15

💡 Hint

Check the 'sum' column at step 3 in the execution_table.

At which step does the loop condition become false?

A Step 6

B Step 4

C Step 5

D Step 3

💡 Hint

Look at the 'Condition (i<5)' column in the execution_table.

If the array had 6 elements instead of 5, how would the loop change?

A The loop would run fewer times

B The loop would not run at all

C The loop would run one more time with i from 0 to 5

D The loop would run infinitely

💡 Hint

Consider the loop condition i < 5 and how it depends on array size.

Concept Snapshot

Arrays store multiple values of the same type in order.
Access elements by index starting at 0: arr[0], arr[1], ...
Use loops to traverse arrays and perform operations.
Loop condition controls how many elements are processed.
Avoid accessing out-of-bounds indices to prevent errors.

Full Transcript

This lesson shows how to work with arrays in C. First, you declare an array and initialize it with values. Then, you use a loop to access each element by its index, starting from 0 up to one less than the array size. In the example, we sum all elements by adding arr[i] to a sum variable inside the loop. The loop stops when the index reaches the array size, preventing out-of-bounds access. The execution table traces each step, showing how the index and sum change. Key points include understanding the loop condition and safe element access. The quiz tests your understanding of these steps and how changing array size affects the loop.