The first 2 pictures below are of the pricey Hewlitt-Packard HP-45, which came out in 1973, and the Texas Instruments SR-50, 1974. I was a high school senior and CUA Aerospace Engineering college freshman in 1974. Being a poor college boy, the TI was much cheaper, so that's what I bought.
And now this stuff is FREE!
|HP-45 (1973) $395|
|TI SR-50 (1974) $170|
|Microsoft Mathematics ver, 4.0 Jan. 2011 On-line (Free!)|