Cray-1

Boots running a hand-authored vector program: it loads two 8-element vectors X and Y into the vector registers V0 and V1, computes the element-wise sum V2 = V0 + V1 and product V3 = V0 * V1, reduces V3 to the dot product X·Y (shown at memory word 040), then bumps X by one and loops — so the vector registers visibly climb every pass. Use the debugger to single-step one instruction (watch V0-V7 fill), set an execution breakpoint on a parcel, or watch a memory word for writes. The on-screen console gives Run / Stop / Step / Reset; press R to run, S to step, "." to stop.