1. CSCI-N 100 Dept. of Computer and Information Science
ABNIAC
CSCI-N 100
Dept. of Computer and Information Science

2. ABNIAC Computer simulator
Uses commands similar to the Elemental Commands
Includes output options

3. Fetch & Execute Cycle
Together, a command list is called the Fetch & Execute Cycle
Computer gets (fetches) a command, executes it and then moves on to the next command

4. The Elemental Commands
Understood by ALL digital computers
Used to manipulate data
Commands (in ABNIAC):
LOAD
STORE
ADD
TEST (COMPARE)
JUMP
Output
ASCII output
HALT

5. The LOAD Command
Take data from a MEMORY slot and put the data into a REGISTER
Opposite of the STORE command

6. The STORE Command
Take data from a REGISTER and put the data into a MEMORY slot
Opposite of the LOAD command

7. The ADD Command Add the values of two REGISTERS
All other arithmetic operations can be derived from add!

8. The COMPARE Command Compare (test) two REGISTER values
Used in conjunction with the JUMP command

9. The JUMP Command
Tells the computer to move to another command in the list of instructions
Used when the computer’s behavior should change based on certain circumstances

10. Output Used to send output to the user
Only parameter the OUTPUT command accepts is the location to output
Information displayed generally an integer

11. ASCII Output One parameter like the OUTPUT command
Instead of an integer, a text character will appear
ASCII representation of the value of that location

12. The HALT Command Indicates the list of commands is finished
Without the HALT, the computer would process until the end of memory is reached – “Out of memory errors”