Introduction:
Importance of input and output operations in assembly language programming
Overview of different input and output methods available in MASM
Console Input:
Reading character input from the console
Handling input errors and checking for special keys
Reading numeric input from the console
Console Output:
Displaying characters and strings to the console
Formatting output using escape sequences
Displaying numeric values to the console
File Input and Output:
Reading from and writing to files in MASM
Opening and closing files
Performing sequential and random access file operations
Example:
assembly
Copy code
.model small
.stack 100h
.data
filename db 'sample.txt', 0
buffer db 100 dup(0)
.code
main proc
mov ax, @data
mov ds, ax
; Console input: Read a character from the user
call readCharacter
; Console output: Display the character
call displayCharacter
; File output: Write the character to a file
call writeToFile
; File input: Read the contents of the file
call readFromFile
; Console output: Display the file contents
call displayString
mov ah, 4Ch
int 21h
main endp
; Procedure to read a character from the console
readCharacter proc
mov ah, 01h
int 21h ; Read character from console
mov buffer, al ; Store the character in buffer
ret
readCharacter endp
; Procedure to display a character to the console
displayCharacter proc
mov dl, buffer ; Move the character to dl
mov ah, 02h
int 21h ; Display character to console
ret
displayCharacter endp
; Procedure to write a character to a file
writeToFile proc
mov ah, 3Ch ; Create or open a file
mov cx, 0 ; Mode: Write
lea dx, filename ; File name
int 21h ; Create or open the file
mov bx, ax ; File handle
mov ah, 40h ; Write to file
mov cx, 1 ; Number of bytes to write
lea dx, buffer ; Data to write
int 21h ; Write the character to the file
mov ah, 3Eh ; Close the file
int 21h ; Close the file
ret
writeToFile endp
; Procedure to read the contents of a file
readFromFile proc
mov ah, 3Dh ; Open the file
mov al, 0 ; Mode: Read
lea dx, filename ; File name
int 21h ; Open the file
mov bx, ax ; File handle
mov ah, 3Fh ; Read from file
mov cx, 100 ; Number of bytes to read
lea dx, buffer ; Buffer to store data
int 21h ; Read the contents of the file
mov ah, 3Eh ; Close the file
int 21h ; Close the file
ret
readFromFile endp
; Procedure to display a string to the console
displayString proc
lea dx, buffer ; Address of the string
mov ah, 09h ; Display string
int 21h ; Display the string
ret
displayString endp
end main
In this example, we demonstrate input and output operations in MASM. We have a buffer variable to store input/output data and a filename variable that represents the name of the file.
First, we read a character from the console using the readCharacter procedure. It uses the int 21h interrupt with function 01h to read a character from the console and stores it in the buffer.
Next, we display the character to the console using the displayCharacter procedure. It moves the character from buffer to the dl register and uses the int 21h interrupt with function 02h to display the character.
Then, we write the character to a file using the writeToFile procedure. It creates or opens the file specified in filename, writes the character from buffer to the file, and then closes the file.
After that, we read the contents of the file using the readFromFile procedure. It opens the file specified in filename, reads the contents into the buffer, and then closes the file.
Finally, we display the contents of the file to the console using the displayString procedure. It uses the int 21h interrupt with function 09h to display the string stored in the buffer.
By understanding input and output operations in MASM, readers gain the ability to interact with users, read and write data to files, and display information on the console. This knowledge allows them to build assembly language programs that can handle user input, process data from files, and present results to the user effectively.
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