What is operator precedence in c programming?

Operator precedence is often associated with order of evaluation, however order of evaluation and operator precedence are actually undefined in C. Expressions may be evaluated in any order while operator precedence is derived from the language grammar. The concept of operator precedence merely simplifies our understanding.

When we think of operator precedence we can imagine a table with 15 rows. When parsing an expression, any operator on a given row takes precedence over those on lower rows. If we also number the rows in ascending order then we can associate each row with a precedence level, such that level 1 has the highest precedence and lower rows have lower precedence.

In addition to precedence, each row also has an associativity. Rows 2, 13 and 14 have right-to-left associativity while all others have left-to-right. For instance, the assignment operator appears on row 14 thus the expression a=b=c is evaluated as if it were actually written a=(b=c) rather than (a=b)=c.