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

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

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

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

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

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

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

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

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

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

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

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”