Some programs for one of the first (and easiest to use) graphing calculators.

Calendar

112 bytes. Uses {A, D, H, M, Y}

Converts input day, month, year to day of week (0=Sun, ..., 6=Sat)

Mastermind

236 bytes. Uses {A, ..., G, M, N, P, ..., Z}

Crack the code in as few goes as possible. Input a 4 digit number(the digits are in the range {0, ..., 5}). Output: a single number. The part before the decimal point tells you the number of digits from your input that are contatined in the code and in the correct position. The part after the decimal point tells you the number of digits from your input that are in the code, but in the wrong position.

Polar Graph

64+ bytes. Uses {I, J, R, S, T, V, W}

Plots a polar graph of a given function r=r(θ) between θ=V and θ=W

Bisection

81+ bytes. Uses {A, B, C, S, X, Y}

Attempts to solve the equation f(x)=0 by the bisection method. The user must input a lower bound (A) and upper bound (B) for the solution.