To convert the mass from kilograms to grams, you can use the conversion factor that 1 kilogram is equal to 1000 grams. Therefore, to convert 4 kg to grams:
\[
4 \, \text{kg} \times 1000 \, \frac{\text{g}}{\text{kg}} = 4000 \, \text{g}
\]
So, a typical laptop computer with a mass of about 4 kg is equivalent to 4000 grams.