Abstract: A gas chromatograph system includes a central processor (CPU) and a printer-plotter. The printer-plotter prints characters and plots data using a single 1 by 7 array of thermal resistors to perform both the printing and plotting operations in real time. The system provides continuous and uniform traces despite changes in the plotting rate.Data from the chromatograph is temporarily stored by the CPU, then forwarded upon programmed command through a print-plot controller to the printer-plotter. Data is plotted as it is received from the CPU. As peaks in the data are detected, plotting is suspended temporarily without loss of data, and characters are printed adjacent to the peaks, thus annotating the peaks with digital data.