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Which INT 21h function would you call if you wanted to make a file read-only?

Which INT 21h function would you call if you wanted to make a file read-only?

Database System Concepts
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
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Which INT 21h function would you call if you wanted to make a file read-only?

Expert Solution
Step 1

The INT 21h function, 7143h, is used to make a file read-only. 

This function involves the data registers, the accumulator and the carry flag.

 

The function is explained with an example as follows. 

 

Step 2

EXAMPLE 

The register AX contains the value 7143h. 
The register BL contains the action code. 

For BL, the action code 00h indicates get attributes and the action code 01h indicates set attributes. 

 

Here, AX is the accumulator. 

BL is the lower half of the 16-bit data register and is an 8-bit data register. 

EAX, ECX, EDX are the 32-bit data registers. 

CF is the carry flag. 

 

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