Suppose we define a service routine starting at memory location x4000. This routine reads in a character and echoes it to the screen. . ORIG x4000 ST R7, SaveR7 GETC OUT LD R7, SaveR7 RET SaveR7 .FILL x0000
Suppose we define a service routine starting at memory location x4000. This routine reads in a character and echoes it to the screen. . ORIG x4000 ST R7, SaveR7 GETC OUT LD R7, SaveR7 RET SaveR7 .FILL x0000
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
Related questions
Question
Machine organization
Question to be answered:
Which instruction (provide a memory address) is executed prior to instructionat locationx4003?
![**Defining a Service Routine at Memory Location x4000**
In this example, we define a service routine starting at memory location x4000. The purpose of this routine is to read a character from the input and then echo it to the screen. Below is the assembly language code for this routine:
```assembly
.ORIG x4000
ST R7, SaveR7 ; Store the content of register R7 into the location SaveR7
GETC ; Read a character from the input and store it in register R0
OUT ; Output the character in register R0 to the screen
LD R7, SaveR7 ; Load the content of SaveR7 back into register R7
RET ; Return from the subroutine
SaveR7 .FILL x0000; Memory location for saving the content of register R7
```
### Explanation of Each Instruction:
- `.ORIG x4000`: This directive indicates that the beginning of the program or routine is at memory location x4000.
- `ST R7, SaveR7`: The content of register R7 is stored into the memory location labeled "SaveR7". This is useful for preserving the value of R7 if it needs to be used within the routine.
- `GETC`: This instruction reads a single character from the keyboard and stores it in register R0.
- `OUT`: This instruction takes the character in register R0 and outputs it to the screen, effectively echoing the character.
- `LD R7, SaveR7`: The previously stored content of register R7 is loaded back into R7 from the memory location "SaveR7".
- `RET`: This instruction returns control to the calling program or the next instruction in sequence.
- `SaveR7 .FILL x0000`: This is a memory location reserved to store the value of R7. ".FILL" is used to initialize this location with the value x0000.
This elementary service routine demonstrates how to handle simple Input/Output operations and register preservation in assembly language programs.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fe019b336-5feb-4f7e-87ed-8ba822dc1cb1%2F091f2e7e-460c-4e4a-8fb8-0bd5f2592289%2Fjredprz_processed.png&w=3840&q=75)
Transcribed Image Text:**Defining a Service Routine at Memory Location x4000**
In this example, we define a service routine starting at memory location x4000. The purpose of this routine is to read a character from the input and then echo it to the screen. Below is the assembly language code for this routine:
```assembly
.ORIG x4000
ST R7, SaveR7 ; Store the content of register R7 into the location SaveR7
GETC ; Read a character from the input and store it in register R0
OUT ; Output the character in register R0 to the screen
LD R7, SaveR7 ; Load the content of SaveR7 back into register R7
RET ; Return from the subroutine
SaveR7 .FILL x0000; Memory location for saving the content of register R7
```
### Explanation of Each Instruction:
- `.ORIG x4000`: This directive indicates that the beginning of the program or routine is at memory location x4000.
- `ST R7, SaveR7`: The content of register R7 is stored into the memory location labeled "SaveR7". This is useful for preserving the value of R7 if it needs to be used within the routine.
- `GETC`: This instruction reads a single character from the keyboard and stores it in register R0.
- `OUT`: This instruction takes the character in register R0 and outputs it to the screen, effectively echoing the character.
- `LD R7, SaveR7`: The previously stored content of register R7 is loaded back into R7 from the memory location "SaveR7".
- `RET`: This instruction returns control to the calling program or the next instruction in sequence.
- `SaveR7 .FILL x0000`: This is a memory location reserved to store the value of R7. ".FILL" is used to initialize this location with the value x0000.
This elementary service routine demonstrates how to handle simple Input/Output operations and register preservation in assembly language programs.
Expert Solution
![](/static/compass_v2/shared-icons/check-mark.png)
This question has been solved!
Explore an expertly crafted, step-by-step solution for a thorough understanding of key concepts.
This is a popular solution!
Trending now
This is a popular solution!
Step by step
Solved in 2 steps
![Blurred answer](/static/compass_v2/solution-images/blurred-answer.jpg)
Knowledge Booster
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.Recommended textbooks for you
![Database System Concepts](https://www.bartleby.com/isbn_cover_images/9780078022159/9780078022159_smallCoverImage.jpg)
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)](https://www.bartleby.com/isbn_cover_images/9780134444321/9780134444321_smallCoverImage.gif)
Starting Out with Python (4th Edition)
Computer Science
ISBN:
9780134444321
Author:
Tony Gaddis
Publisher:
PEARSON
![Digital Fundamentals (11th Edition)](https://www.bartleby.com/isbn_cover_images/9780132737968/9780132737968_smallCoverImage.gif)
Digital Fundamentals (11th Edition)
Computer Science
ISBN:
9780132737968
Author:
Thomas L. Floyd
Publisher:
PEARSON
![Database System Concepts](https://www.bartleby.com/isbn_cover_images/9780078022159/9780078022159_smallCoverImage.jpg)
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)](https://www.bartleby.com/isbn_cover_images/9780134444321/9780134444321_smallCoverImage.gif)
Starting Out with Python (4th Edition)
Computer Science
ISBN:
9780134444321
Author:
Tony Gaddis
Publisher:
PEARSON
![Digital Fundamentals (11th Edition)](https://www.bartleby.com/isbn_cover_images/9780132737968/9780132737968_smallCoverImage.gif)
Digital Fundamentals (11th Edition)
Computer Science
ISBN:
9780132737968
Author:
Thomas L. Floyd
Publisher:
PEARSON
![C How to Program (8th Edition)](https://www.bartleby.com/isbn_cover_images/9780133976892/9780133976892_smallCoverImage.gif)
C How to Program (8th Edition)
Computer Science
ISBN:
9780133976892
Author:
Paul J. Deitel, Harvey Deitel
Publisher:
PEARSON
![Database Systems: Design, Implementation, & Manag…](https://www.bartleby.com/isbn_cover_images/9781337627900/9781337627900_smallCoverImage.gif)
Database Systems: Design, Implementation, & Manag…
Computer Science
ISBN:
9781337627900
Author:
Carlos Coronel, Steven Morris
Publisher:
Cengage Learning
![Programmable Logic Controllers](https://www.bartleby.com/isbn_cover_images/9780073373843/9780073373843_smallCoverImage.gif)
Programmable Logic Controllers
Computer Science
ISBN:
9780073373843
Author:
Frank D. Petruzella
Publisher:
McGraw-Hill Education