The line input file is used to control how and when calculations are performed. Three different types of input command lines are recognised in an Xtal input file. System command lines signal certain nucleus functions; program initiation lines initialize specific calculations; and program data lines are used to enter data for a calculation.
The system command lines are:
| title | specify the output print header |
| compid | set the compound identification code |
| master | set master file switch and specify filenames |
| remark | insert comments into the printed output |
| copybdf | copy a binary file |
| reset | reset printer parameters |
| setid | specify a default line identifier |
| field | fix the format of input lines |
| order | reorder fields of input line data |
| finish | end of the input line file |
This line contains a character string to be inserted at the top of each printed page. Only one title line is active at a time, but any number may be entered during a sequence of calculations. STARTX stores the current title image in the archive file record lrlabl:.
Field 1- character string, columns 8 to 72. Default string is blank.
This line is used to set the compound identification code for the data under study. See the compid discussion below in 3.
Field 1 an alphanumerical string of up to six characters.
This line is used to control the use of the master archive file. The default master file condition is set on installation with the masterfile: macro. This line enables the user to specify master file support for the current run. A master line, if entered, must precede the first program initiation line. The following free format controls may be used:
no switch master file support off; no master files are read or written
yes switch master file support on; master files read & written from aaa
read v copy a master archive file with extension v to the binary file aa1
write w copy the latest binary file to a master archive file with extension w
This line contains a character string to be output to the print file. Unlike the title line, it is output only once and is output as soon as it is encountered in the input. An example follows at the end of this section.
Field 1- character string, columns 8 to 72. Default string is blank.
This line is used to copy one binary data file (bdf) to another, The syntax of this command is: 'copybdf <ext1> <ext2>'. The binary file with extension ext1 is copied to a binary file with extension ext2. The extension codes are user choice, and need not be any of the extensions described above. The purpose of this command is enable the user to save or retrieve a binary file during an Xtal run. Note, however, that a copybdf line can only be used after the compid line or an end line.
If the codes a or b are used as extension codes, they will be interpreted as the current input or output archive binary file, respectively. In other words, the extension aa1 or aa2 will be substituted where appropriate. Typical uses of this command follow:
This line resets certain Xtal input/output functions. The prime use of this command is to redefine the printer characteristics for a given run. This is particularly useful in a networked computing environment. The syntax of the reset command consists of a parameter code followed by a numerical parameter.
This line is used to preset the identification code of the lines which follow. This may be used to read non-Xtal formatted lines. Once the setid has been entered, all succeeding lines, except the system commands, are treated as having the identification code specified on the setid line, until another setid is read. When setid is in force, the field 1 of a line starts in column 1 of the input line (this is field 0 when setid is not in force).
This line specifies the format of fields for input lines that follow. The input numbers specify the rightmost character of successive fields. The leftmost character of each field is assumed to be rightmost character number of the previous field, +1. The leftmost character of field 1 is character 1. If an identification code is entered on an input line which has been formatted by a preceding field line, an order line will need to be also specified so that this field can be ignored or properly treated. All fields expected as input must be specified on the field line. A blank field line is used to reset to free format input.
This line specifies the order of fields for input lines that follow. This enables the input fields of either fixed or free format lines to be re-ordered to match the requirements of the inputting program. This facility is particularly useful for reading non-Xtal lines in which data must be reordered or ignored to meet Xtal program requirements. A blank order line resets the order to sequential.
The first example shows the simplest use of system command lines.
title This line appears at the top of each printed page remark These lines appear only once in the printout reset cmax 80 :reset printer line width master yes read zzz :use the master file compid.zzz |
The next example is more complicated. It shows how a set of input lines containing the atom information may be input as if they were atom lines (these data lines are used by many programs -- see ADDATM). The blank setid and order lines are necessary to restore line identification and field ordering to default values.
A 'program initiation' line is used to initiate an Xtal calculation. These lines contain the program identifer code which is used to identify each program in the Xtal documentation and in the nucleus routine AA00. For example, a line containing FC (as characters 1-2) initiates the structure factor calculation. The program initiation line may also contain input parameters. Any additional input data is entered on separate 'program data' lines. These are described below.
A 'program data' line is used to enter data under the control of a specific program. Each data line starts with a code which uniquely identifies its function. This code is used by the program to identify the data. The order that data lines are entered may be arbitrary or it may be fixed. The entry rules for each data line are given in the Program controls section. If a program data line is mandatory its name is capitalised, whereas optional data lines are in lower case. Note also that the requirement to input some data lines may be dependent on the presence of others.
The majority of input lines, and parameters, used by Xtal programs are optional. The default for each program are set at their most commonly used values. In the Program controls section of this manual default values are indicated iether with a dotted underline or in red (e.g. sinv ), or as italicised numbers or characters on the right hand side of the line (e.g. 1000). Unless the user needs to specify a different value, these parameters or lines need not be entered.
The last data line for a given calculation is followed by one of the following: an end line; another program initiation line; a finish line; or an end-of-file.