i do plc programming for living (AB, Omron, Mitsubishi, Siemens, Modicon etc.).
as one of the earlier posts states you will need programming software
package (it is not always just one program) for particular model and proper programming interface (often just a cable but not always). Most of the plcs are programmed in ladder logic while there are other languages off course. For example you can get PLCs nowdays that can be programmed in a mix of languages like ladder, function block, structured text, sequence flow chart etc.
software packages differ in functionality and price (often few thousand dollars per licence although there are cheaper ones like from Automation Direct etc.). This is what makes you really concerned about your laptop.
You might loose (or have it stolen) your precious $4k Dell - but it's the $15-50k worth of software installed on it that makes the loss significant (depending on how many platforms you have to support).
You can go to
www.meau.com and download GX Developer 8.xx for free. It will work without licence for 15 days (after that you'll have to lighten your wallet). It will give you good idea what's plc programming like.
on the light side, there are so called "smart relays" that have only few I/O. they can normally be programed using tiny LCD and buttons on front of the unit (Lego, Alpha etc.). what do you have?