Nascom News­let­ter

straightforward.

Should the two specified portions of memory overlap, the effect of the command is to ‘rotate’ the contents of a section of memory. The memory section which is rotated is determined by: (i) the lower of the two start addresses, (ii) the higher of the two start addresses, plus the specified length, minus one.

The memory addresses at the two limits are included in the rotation. Rotation occurs in a downwards direction with the overflow from the lowest address being wrapped around to the highest address.

AAAA – start address of the first portion of memory.
BBBB – start address of the second portion of memory.
CCCC – length of memory (bytes) to be exchanged.

Converts a decimal integer in the range minus 32768 to plus 65535 to hexadecimal.

If the number to be converted is negative, a minus sign should be typed immediately before the first digit of the decimal number. The number itself may only contain the digits 0 through 9.

The result of the conversion to hexadecimal is displayed on the first screen line following the command letter. The result is always displayed as a four digit hexadecimal number. In addition, if the value can be represented by a single byte, a two digit hexadecimal number is also displayed on the same line. Note: If a positive value is entered, it should be remembered that hexadecimal equivalents which start with a digit greater than 7, may also be interpreted as negative values.

The decimal number to be converted is supplied on the same line as the ‘d” command. The value may be preceded by spaces and is terminated either by the first following space or by the end of the line, whichever occurs first.

Values from the NAS-SYS arguments are not used by this command. Also, values which are entered on the command line are not placed into the NAS-SYS arguments (ARG1 through ARG10). However, NUMV is set to the hexadecimal value and NUMN is set to the number of decimaligits entered.

-AAAAA – decimal number for conversion in the range −32768 to 65535

The actual conversion is quite straightforward. The routine examines the decimal digits from left to right. The result register is initially set to zero. The next digit is then added to the ‘result’ and, unless it is the rightmost digit, a copy of the ‘result’ is added to the ‘result’ further nine times (i.e. multiplication by ten). This process is repeated until all of the input digits have been processed. As the arithmetic is all done in hexadecimal, the result is in hexadecimal.