Type Conversions (C)
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Type conversions depend on the specified operator and the type of the operand or operators. Type conversions are performed in the following cases:
When a value of one type is assigned to a variable of a different type or an operator converts the type of its operand or operands before performing an operation
When a value of one type is explicitly cast to a different type
When a value is passed as an argument to a function or when a type is returned from a function
A character, a short integer, or an integer bit field, all either signed or not, or an object of enumeration type, can be used in an expression wherever an integer can be used. If an int can represent all the values of the original type, then the value is converted to int; otherwise, it is converted to unsigned int. This process is called "integral promotion." Integral promotions preserve value. That is, the value after promotion is guaranteed to be the same as before the promotion. See Usual Arithmetic Conversions for more information.