How to Take Input From User in Assembly Language
The 8086 assembly language allows the programmer to take input from the user. This is done with the “input” instruction. The user types a number, and the program prints out the result. For example, if a user types the number “1” he gets the result “2” and so on. This is done using the “input” instruction and the stack. An 8086 assembly language program can also take input from the user by using the interrupt method. This allows the programmer to loop until the user presses Enter.
When programming in assembly language, it is important to be aware of memory location and offset values. Memory addresses are relative to the starting address of a segment, which is a hexadecimal value equal to 16. In 8086, the starting addresses are stored in the “segment registers”. When the program wants to access memory data, it needs an offset value, which is also called “displacement.” Once the processor has the address, it will combine the address and offset value to retrieve the data it requires.
Assembler code will assume a 32-bit address and segment. Word operations will be preceded by a 16-bit data prefix byte. Unless specified otherwise, items inside square brackets are optional; items inside parentheses are required. Also, when using the sreg prefix, the offset component must be a colon before the instruction.
Assembler code requires the use of the operating system API and will require a keyboard input and output. The difference between assembler code and a programming language lies in the fact that assembler code does not tell the programmer what to do. A programmer must use the operating system API to make sure his program works well.
Another difference between assembly language code and C++ code is the use of macros. Macros are a great way to create modular assembly language code. This way, macros are created and used wherever they’re needed. If you create a macro for an instruction, you can call it anywhere you need it, including other procedures.
The INT 21h call is another way to take input from the user. This call has a number of parameters that need to be passed from the CPU. These include taking input, showing output, controlling the mouse, and accessing vga memory. The CLEAR_SCREEN procedure will clear the screen and set the cursor to the top of the screen.