C study notes[3]

魔力之心2025-07-26 20:32

operatons

the fundamental operators such as +,-,* in C language can be simply manipulated.

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int sum = 5 + 3;  // sum = 8
int difference = 10 - 4;  // difference = 6
int product = 6 * 7;  // product = 42

the operator / was left to introduce just a moment because that it's special as follows.

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5/2=2
5.0/2.0=2.5
5/2.0=2.5

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int quotient = 15 / 4;  // quotient = 3 (integer division)
float result = 15.0 / 4;  // result = 3.75

the operator % can get the remainder after division

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int remainder = 15 % 4;  // remainder = 3

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int x = 1;
int y= x++;

as similar principle, -- apply the compuation of decreasing by 1 by itself.

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int x = 1;
int y= x--;

--x and ++x mean that the final result is returned affter these operation have finished.

The sizeof operator is a compile-time unary operator that returns the size (in bytes) of a variable, data type, or expression.

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sizeof(type)
sizeof(expression)
sizeof variable_name

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int i = 0;
while (i < 5) {
    printf("%d ", i);
    i++;
}
// Output: 0 1 2 3 4

do-while loop:as similar as while,the condition of loop which is true decides to continue loop but there is an obvious difference that the do-while loop inspects the loop's condition after finishing the block of the loop one time ,no matter whether the condition was met .

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int i = 0;
do {
    printf("%d ", i);
    i++;
} while (i < 5);
// Output: 0 1 2 3 4

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for (int i = 0; i < 5; i++) {
    printf("%d ", i);
}
// Output: 0 1 2 3 4

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for (int i = 0; i < 10; i++) {
    if (i == 5) break;
    printf("%d ", i);
}
// Output: 0 1 2 3 4

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for (int i = 0; i < 5; i++) {
    if (i == 2) continue;
    printf("%d ", i);
}
// Output: 0 1 3 4