Nested Loops

Nested Loops

Put a loop inside a loop, and you get a nested loop - the inner loop runs fully for each step of the outer one.

The pattern

for (int i = 1; i <= 2; i++) {
    for (int j = 1; j <= 3; j++) {
        printf("i=%d j=%d\n", i, j);
    }
}

Output:

i=1 j=1
i=1 j=2
i=1 j=3
i=2 j=1
i=2 j=2
i=2 j=3

How it runs

• The outer loop moves slowly: i = 1, then i = 2.
• For each outer step, the inner loop completes fully.

Total runs

Outer rounds (2) times inner rounds (3) = 6 total prints. Multiply to predict the count.

Real uses

• Printing tables, grids, and matrices.
• Comparing pairs of items.
• Many array patterns.

TL;DR

• Nested = inner loop repeats fully inside each outer step.
• Total runs = outer count x inner count.
• Great for grids and tables.
• Mind the braces and indentation.