If the A-register contains zero, the current sequence of control is terminated and a new sequence is begun at location yy. The next instruction to be executed is contained in memory location yy. If the A-register contains a non-zero number, the current sequence of control continues. The contents of all memory locations and the A- and Q-registers are unchanged by this instruction. This is one of the two instructions in RAMM called conditional transfer instructions. A branch is made on the condition that the A-register contains zero at that point in the program. The mnemonic AZJ could represent "A-Register is Zero, Jump."

Example: Suppose that the contents of the A-register are zero and the following instruction sequence with memory addresses as listed appears in a program:

If we pick up program execution at memory location 45 in this example, since the contents of the A-register are zero, a transfer of control is made to memory location 50 for the next instruction. A new sequence of control is begun at location 50. If the contents of the A-register had not been zero when the AZJ instruction was encountered then the next instruction executed after location 45 would have been the instruction at location 46.

If the A-register contains a negative number, the current sequence of control is terminated and a new sequence is begun at location yy. The next instruction to be executed is the contents of memory location yy. If the A-register contains a positive number or zero, the current sequence of control continues. The contents of all memory locations and the A- and Q-registers are unchanged by this instruction. The mnemonic AMJ stands for "A-Register Minus, Jump." The AMJ instruction is one of two conditional branch instructions in RAMM.

Using the AZJ and AMJ instructions together allows you to implement three branches of a decision symbol in a flowchart. Compare value A to value B by computing A - B, leaving the result in the A-Register.

A combination of AZJ and AMJ can check the case of a positive result since if the result is not zero or negative, then it must be positive.

Example: Suppose that the following instruction sequence is given with memory locations as indicated and suppose that the A-register currently contains a negative number.

If we pick up the program execution at memory location 60, then the next instruction to be executed is at memory location 72. A new sequence of control is begun at 72. If the A-register had not contained a negative value at this point in the program then the next instruction executed after the AMJ instruction would have been at memory location 61.

Example: Compare two values and make a branch based upon this comparison. Suppose that we have the following memory contents and instructions listed below:

Suppose that we pick up program execution at location 20. Here we are comparing the contents of location 10 to the contents of location 11. The result in the A-register after execution of the ISB instruction at location 21 would be 0003. Since this is not a negative value the branch specified by the AMJ instruction at location 22 would not be taken and since the A-register is not zero the branch specified by the AZJ instruction at location 23 is also not taken. Thus the next instruction executed after this sequence of steps is the instruction at memory location 24. This is an example of using AMJ and AZJ instructions together to get the net effect of "A-Register Positive, Jump" function. We don't need an APJ because we use AMJ and AZJ together to achieve the same result.

This instruction causes no operation to be performed. The current sequence of control continues. The operand yy is ignored during the execution of the instruction. The purpose of the NOP is to allow the programmer to place one or more "do nothing" instructions in a sequence of program code. In subsequent revisions of the program, the programmer may wish to replace these NOP instructions with other code. The "do nothing" instructions may also be used as "place holders" for instructions to be computed or modified during execution. The ability of the programmer to cause the program to dynamically change itself during execution is one of the most powerful techniques available in machine language programming.Example: Suppose the following code segment is given at the memory locations indicated and that execution begins at memory location 33.

This code caused the contents of memory location 04 to be added to the contents of memory location 05 and the sum stored in memory location 07. Execution of the NOP instruction at location 36 causes no change in the registers or memory locations and the sequence of control would pass on to memory location 37.

This instruction reads a decimal integer from the input stream (either a data file or value input through the keyboard) and stores the value in the memory location whose address is yy. The initial contents of yy are destroyed and the contents of the A- and Q-registers are unchanged. The RDI instruction allows us to input values in an executing program. The value read in replaces the value currently stored in memory location yy.

Example: Suppose that the following memory contents are given at the memory locations indicated:

If we pick up program execution at location 35, the RDI instruction will request that you input a value by displaying a dialog box on the screen with the message: "Input a value." You should input a data value in the range -999 to 9999. If you input the value 0345 through the keyboard, then after execution of the RDI instruction, the contents of memory location 10 would be 0345.

This instruction prints on the next output line the integer stored in memory location yy. The contents of yy and the A- and Q-registers are unchanged. The PRI instruction produces output by listing the address of the memory location to be printed out and then the contents of that memory location, for example "(96) = 0012" would be generated by the instruction 6696 if memory location 96 contained the value 0012. The PRI instruction is the only means to output values from a RAMM program. Note that the only values that can be printed are 4-digit decimal integers.

Example: Suppose that the following code sequence is given with memory contents as indicated:

If we pick up program execution at memory location 35, the PRI instructions would cause the following output to be listed on the screen:

This instruction terminates the current sequence of control and starts a new sequence at memory location yy. The next instruction to be executed is the contents of yy. The contents of all memory locations and the A- and Q-registers are unchanged by this instruction. We also call this instruction an unconditional branch instruction. The current sequence of control in a program is that order of execution in which, when the current instruction has finished executing, the next instruction to be executed is stored in the next consecutive memory location. The UNJ instruction is one of three instructions that can cause a transfer of control in a program.

Example: Suppose we are given the following instruction sequences located at the memory locations indicated:

This instruction indicates the end of the program loading operation and also specifies that execution of the program is to begin at memory location yy. The END instruction is the last instruction of any RAMM program. Since END is processed during the program-loading phase, that is, the phase where the program is stored into the RAMM computer memory, it cannot be considered an executable instruction. The HLT instruction is used to terminate execution of the program while the END instruction is used to terminate loading of the program. If the END instruction is encountered during execution of a program, the 99 operation code causes termination of processing with an error message that an illegal operation code was encountered.

Example: Suppose that the following code sequence is given:

As the RAMM program is loaded into memory of the RAMM computer the instruction that is loaded into memory location 70 causes the loading operation to be terminated. Notice that the HLT instruction in location 69 was not recognized as a halt at the time that the program was loaded into the RAMM computer memory since the only instruction that is actually processed during the program loading phase is the 99 (END) instruction. After the END instruction is processed the program will begin execution at memory location 02 when the programmer specifies that he wishes to "run" or execute the program.

END in Assembly Language

The END pseudo-instruction signifies the end of a program and must be the last statement in the program. The instruction terminates the assembly (translation) process and also the loading process. If no fatal assembly errors have occurred execution will begin at memory location yy when the programmer specifies that he wishes to "run" or execute the program. If yy is omitted, execution begins at location 00. A symbol in the location field is illegal.

The BSS pseudo-instruction reserves k consecutive memory locations starting at the current location. The contents of the locations reserved are not altered by this instruction. The constant k must be an unsigned RAMM constant. If k=0, the symbol occurring in the location field is assigned to the current location but no memory location is reserved.

The DEC pseudo-instruction stores the (decimal) RAMM constant k in the current location. If a symbol occurs in the location field, it is assigned to the current location.