The following data types are readable for a PLC-5.

Type	Meaning
O	Output table
I	Input Table
S	System Status
B	Binary
T	Timer
C	Counter
R	Control
N	Integer
F	Float
A	ASCII
BT	Block Transfer Control
D	BCD
L	Long Integer
MG	Message Control
PD	PID Control
SC	??
ST	String


I have also added a few more to deal with non-data table stuff:
PN 8	Program Name -  will return the PLC name - always 8 bytes.
RGx:y	Rung Data - x = file number, y = element (not rung) number.  Will
	return 1 element at a time unless more requested.
FO:x	Force Output Table - word x
FI:x	Force Input Table - word x
XAx:y	Section 3 data, subsection x, element y.
XBx:y	Section 4 data, subsection x, element y.
XCx:y	Section 5 data, subsection x, element y.
XDx:y	Section 6 data, subsection x, element y.


