I want to acquire a practical book (for dummies) on 'how to connect my
pc to external objects like motors, thermometers, cameras, actuators,
etc. and control/read them in realtime by means of Borland Pascal
programs'.  Info on the book's title, author, price and seller  gets
the cash.  Remember level of book 'dumb' but not 'dumber' and must be
in print.

Basically any pascal manual that includes serial communication can
give you those answers, the trick is in interpreting the data coming
from the device not the other way arround.

Hence you would need a manual of the device you are attaching and see
what kind of information it sends out , then write a program that can
interpret the data

Thank you for your comment Corwin02-ga. I understand what you say but
my needs are more basic than that, like on the level of 'how do you
connect the pc to the device'.

Shred-ga

Usually you use the serial port of your computer to attach to a device
(provided the device has an output port of sorts to start with)

pin assigments on an RS 232 port are as follows 

9 pin 

1 DCD (data carrier detect)
2 RD  (receive data)
3 TD  (transmit data)
4 DTR (Data Terminal Ready)
5 GRD (Signal Ground)
6 DSR (Data set ready)
7 RTS (request to send)
8 CTS (clear to send)
9 RNG (Ring indicator)

25 pin

1  PGRD (protective Ground) 
2  TD
3  RD
4  RTS
5  CTS
6  DSR
7  GRD
8  DCD  
9  Test Pin
10 Test pin
11 
12 DCD(2)
13 CTS(2)
14 TD(2)
15 DCE (transmitter clock) 
16 RD(2)
17 RCLK (Receiver Clock)
18 
19 RTS(2)
20 DTR
21 SQ  (Signal Quality) 
22 RNG
23 DSR (Data Signal rate detector)
24 DTE (Transmitter Clock) 
25 DCD

Since 25 pin connectors are rare nowadays I will concentrate on the 9
pin connector
The simplest connection to monitor/control a device is a simple null modem cable 

2----3
3----2
5----5

Some Devices require something a little more elaborate being a null
modem cable with loop back handshaking
2------3
3------2
5------5
1-    -1 
  |  |
4-    -4
7-    -7
  |  |
8-    -8

(sorry for the ascii art but that is all that is available)

there are two more designs for handshaking (Partial and Full) but
those are hardly ever used

Now all your program has to do is interpret the signal coming in on
pin 2 and 3 (basic capture of the data) and if need be send out a
signal on those two pins