The AT24C256 is a 32K byte, 8-pin EEPROM IC. As we know EEPROM stands for Electrically Erasable Programmable Read-Only Memory, we can store information on this IC and it will remain there even when the power is turned off just like your pen drive.
DAC0808 is a D/A converter IC and is used for converting 8 bit digital data input to analog signal output. It is a monolithic IC featuring a full scale output current settling time of 150 ns while dissipating only 33 mW with ±5V supplies.
LM339 is a voltage comparator IC from LMx39x series and is manufactured by many industries. The devices consist of four independent voltage comparators that are designed to operate from a single power supply.
DAC7715 is a ‘Digital to Analog Converter’ chip designed by Texas Instruments and is available in SOIC-16 package only. The chip takes in 12 bit serial data and provides analog output at any one of selectable four output channels.