PIC Serial Programmer
Those are the lines you need to control, but that's a really crappy and primitive programmer.  Do yourself two favors:

Return the 16F84 to whatever museum it came from.  Even if you want to stick to a small microcontroller like that, at least use one of the newer PIC 16F1xxx series.  They all do more, cost less, and don't need 13 V on MCLR to enter programming mode.

Get a programmer instead of making one.  What you are doing is like saying you want to learn cabinet making, but are trying to start by building your own hammer.  Just buy the hammer and get on with what you really want to do.  Really simple PIC programmers, like ones that abuse serial ports as you show, can be made to work, but will also have issues so that when things aren't working you don't know if the programmer is part of the problem.



My LProg PIC programmer follows all the rules and specs, and works with the 3.3 V parts that don't need high voltage on MCLR to enter programming mode.  At $20, it just isn't worth trying to re-invent that hammer.  Also take a look at the Microchip PicKit3.  It's a little more money, but can also work as a debugger.