The title of this page refers to the ability to input data from a data source such as the keyboard directly into a C program variable without the need to press <enter>. The act of inputting a single ascii character into a char variable such as "char choice;" is simple.
The act of immediate input of data into say an int variable raises some issues such as what is the end of transmission indicator. The author supports the assertion that any non-integer character may be used to indicate "end of incoming integer. This assertion needs further testing.
The short program available for download illustrates several examples of inputting data directly into a program variable without waiting for the <enter> key to be pressed.