There are four different formats used for ORTEP instructions, which are numbered 0, 1, 2, and 3. Format No. 0 is always used for a new instruction and includes the instruction number. Some instructions require trailer (continuation) cards, which use format numbers 1, 2, and 3. The program is informed what the format of the next card will be with the value in the look ahead field, columns 1-3. The program action is also influenced by this information.
on current card
|Next card will be||Program action|
|0 or blank||Format No. 0, a new instruction||Execute present instruction; then read next new instruction card|
|1||Format No. 1, continuation of present instruction||Read continuation card and then check its "Look ahead"|
|2||Format No. 2, continuation of present instruction||Read continuation card and then check its "Look ahead"|
|3||Format No. 3, alphanumeric information||Read alphanumeric information and execute instruction; then read next new instruction card|
The Format No. 0 instruction card and the Format No. 1 parameter continuation card have the FORMAT (I3,I6,7F9.0), but the former includes the instruction number while the latter does not. A maximum of 19 Format No. 1 continuation cards per instruction is permitted.
|Columns||Format No. 0
|Format No. 1
Parameter Continuation Card
|3||"Look ahead" (0,1,2,3)||"Look ahead" (0,1,2,3)|
|10-18||1st parameter||8th parameter
or 15th, ..., or 134th
|19-27||2nd parameter||9th parameter
or 16th, ..., or 135th
|64-72||7th parameter||14th parameter
or 21st, ..., or 140th
The Format No. 2 trailer card is also used for parameter continuation, but it is more compact with FORMAT (I3,6X,5I3,8F6.0), allowing more information to be entered than on the Format No. 1 card. Many, but not all, Format No. 2 trailer cards include vector search codes, and they are often referred to as Vector Search Code (VSC) cards. A maximum of 20 Format No. 2 continuation cards per instruction is permitted.
|Columns||Format No. 2
Parameter Continuation Card
|3||"Look ahead" (0,1,2,3)|
|10-12||1st integer parameter|
|22-24||5th integer parameter|
|25-30||1st real parameter|
|67-72||8th real parameter|
Format No. 3 trailer cards with FORMAT (18A4) are used for entering label information and are required for instructions 902, 903, and 913. As a trailer to these, they may contain up 72 characters of alphanumeric information in columns 1-72. The information should be centered about columns 36 and 37, or it should begin in column 1 for automatic centering. These may also be used with other instructions as a device to transfer comments about the particular instruction to the ORTEP output listing. There is no look ahead column in Format No. 3; the next card must be a new instruction card.
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Page last revised: March 7, 1996