What are the abbreviation representation for scientific calories, food calories and SI units of energy?

Answer 1

I don't know how standard this is but I've always used cal for calorie for science and kcal for kilocalorie for science.
Food calories are called calories but the calories we count when we eat and read about in diets actually are kilocalories. Many nutritionists differentiate by calling the calorie a SMALL calorie and using a lower case c for that or a LARGE calorie or BIG calorie and using an upper case C. Therefore, a C actually is a kilocalorie. In science (SI), energy is measured in joules with 4.184 joules = 1 calorie (1 small calorie). The SI abbreviation is J.