C Primer Plus®, Third Edition

More Assignment Operators: +=, −=, *=, /=, %=

C has several assignment operators. The most basic one, of course, is =, which simply assigns the value of the expression at its right to the variable at its left. The other assignment operators update variables. Each is used with a variable name to its left and an expression to its right. The variable is assigned a new value equal to its old value adjusted by the value of the expression at the right. The exact adjustment depends on the operator, for example,

scores += 20	is the same as	scores = scores + 20
dimes −= 2	is the same as	dimes = dimes − 2
bunnies *= 2	is the same as	bunnies = bunnies * 2
time /= 2.73	is the same as	time = time / 2.73
reduce %= 3	is the same as	reduce = reduce % 3

In the preceding ...