How many times does this loop? mov cx, 5 mov bx, 0 L1: dec cx inc bx jnz L1

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
Problem 1PE
icon
Related questions
Question
### Understanding Loop Execution in Assembly Language

In this example, we will analyze a simple loop written in Assembly language to determine how many times it executes.

```assembly
mov cx, 5      ; Initialize register CX with 5
mov bx, 0      ; Initialize register BX with 0

L1:            ; Label L1
    dec cx     ; Decrement CX by 1
    inc bx     ; Increment BX by 1
    jnz L1     ; Jump to L1 if CX is not zero
```

#### Explanation:

1. **Initialization**:
    - The instruction `mov cx, 5` sets the register `CX` to 5.
    - The instruction `mov bx, 0` sets the register `BX` to 0.

2. **Loop Execution**:
    - The label `L1` marks the beginning of the loop.
    - The instruction `dec cx` decrements the value in `CX` by 1.
    - The instruction `inc bx` increments the value in `BX` by 1.
    - The instruction `jnz L1` checks if `CX` is not zero; if true, it jumps back to label `L1`. If `CX` is zero, the loop terminates.

3. **Iteration Count**:
    - The loop continues until the value in `CX` is decremented to zero. Since `CX` starts at 5 and is decremented by 1 in each iteration, the loop executes 5 times.
    - During each iteration, `BX` is incremented by 1. 

After 5 iterations, `CX` will be 0, causing the `jnz L1` instruction to fail its condition and terminate the loop. At this point, `BX` will have been incremented from 0 to 5.

#### Conclusion:

The loop executes **5 times**.

By understanding the flow of this simple Assembly loop, one can gain insights into the basic operation of loops in low-level programming.
Transcribed Image Text:### Understanding Loop Execution in Assembly Language In this example, we will analyze a simple loop written in Assembly language to determine how many times it executes. ```assembly mov cx, 5 ; Initialize register CX with 5 mov bx, 0 ; Initialize register BX with 0 L1: ; Label L1 dec cx ; Decrement CX by 1 inc bx ; Increment BX by 1 jnz L1 ; Jump to L1 if CX is not zero ``` #### Explanation: 1. **Initialization**: - The instruction `mov cx, 5` sets the register `CX` to 5. - The instruction `mov bx, 0` sets the register `BX` to 0. 2. **Loop Execution**: - The label `L1` marks the beginning of the loop. - The instruction `dec cx` decrements the value in `CX` by 1. - The instruction `inc bx` increments the value in `BX` by 1. - The instruction `jnz L1` checks if `CX` is not zero; if true, it jumps back to label `L1`. If `CX` is zero, the loop terminates. 3. **Iteration Count**: - The loop continues until the value in `CX` is decremented to zero. Since `CX` starts at 5 and is decremented by 1 in each iteration, the loop executes 5 times. - During each iteration, `BX` is incremented by 1. After 5 iterations, `CX` will be 0, causing the `jnz L1` instruction to fail its condition and terminate the loop. At this point, `BX` will have been incremented from 0 to 5. #### Conclusion: The loop executes **5 times**. By understanding the flow of this simple Assembly loop, one can gain insights into the basic operation of loops in low-level programming.
Expert Solution
steps

Step by step

Solved in 3 steps

Blurred answer
Knowledge Booster
Load Event
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, computer-science and related others by exploring similar questions and additional content below.
Similar questions
Recommended textbooks for you
Database System Concepts
Database System Concepts
Computer Science
ISBN:
9780078022159
Author:
Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:
McGraw-Hill Education
Starting Out with Python (4th Edition)
Starting Out with Python (4th Edition)
Computer Science
ISBN:
9780134444321
Author:
Tony Gaddis
Publisher:
PEARSON
Digital Fundamentals (11th Edition)
Digital Fundamentals (11th Edition)
Computer Science
ISBN:
9780132737968
Author:
Thomas L. Floyd
Publisher:
PEARSON
C How to Program (8th Edition)
C How to Program (8th Edition)
Computer Science
ISBN:
9780133976892
Author:
Paul J. Deitel, Harvey Deitel
Publisher:
PEARSON
Database Systems: Design, Implementation, & Manag…
Database Systems: Design, Implementation, & Manag…
Computer Science
ISBN:
9781337627900
Author:
Carlos Coronel, Steven Morris
Publisher:
Cengage Learning
Programmable Logic Controllers
Programmable Logic Controllers
Computer Science
ISBN:
9780073373843
Author:
Frank D. Petruzella
Publisher:
McGraw-Hill Education