Hex Notation in Computing: Understanding the Basics
What will be the content of variables A, B, the WREG, and the states of the status bits Z and C after execution of the following instructions?
The given code snippet consists of three instructions:
- movf A, W: This instruction moves the contents of variable A to the WREG (Working Register).
- addwf B, W: This instruction adds the contents of variable B to the WREG.
- movwf A: This instruction moves the contents of the WREG to variable A.
Write the answers in hex notation.
Answer:
WREG = 0x00
A = 0x00
B = 0x80
Z = 1
C = 1
The provided code snippet involves manipulating the contents of variables A and B using hexadecimal notation. Let's break down the instructions and analyze the resulting values:
movf A, W:
This instruction moves the content of variable A (0x80) to the WREG. Therefore, the WREG now contains 0x80.
addwf B, W:
Next, the contents of variable B (0x80) are added to the WREG, resulting in a total of 0x100. However, in hexadecimal notation, the value 0x100 is represented as 0x00 due to the limited space for representation. As a result of the addition, the Carry (C) flag in the status register is set to 1.
movwf A:
Finally, the content of the WREG (0x00) is moved back to variable A. Therefore, variable A now holds the value 0x00.
To summarize:
- WREG = 0x00
- A = 0x00
- B = 0x80
- Z = 1 (indicating that A is now 0)
- C = 1 (due to the carry generated during addition)
Hexadecimal notation, or hex notation, plays a crucial role in computing by providing a compact and human-readable way to represent binary data. Each hexadecimal digit corresponds to four bits, making it a convenient system for expressing byte values and other binary information. Understanding hex notation is essential for working with low-level programming languages, digital systems, and various aspects of computer science.